How do I disable a system device programmatically?

Looks like there were two things in drf's version that were giving you trouble. Your x64 problem was caused by SP_DEVINFO_DATA having a uint where an IntPtr was needed. The second is that the SetupDiGetDevicePropertyW function is Vista+ and won't run on XP.

Here's a version with those two issues corrected. I tested as x86 and AnyCPU on XPx86 and Win7X64.

public static class DisableHardware
{
    const uint DIF_PROPERTYCHANGE = 0x12;
    const uint DICS_ENABLE = 1;
    const uint DICS_DISABLE = 2;  // disable device
    const uint DICS_FLAG_GLOBAL = 1; // not profile-specific
    const uint DIGCF_ALLCLASSES = 4;
    const uint DIGCF_PRESENT = 2;
    const uint ERROR_INVALID_DATA = 13;
    const uint ERROR_NO_MORE_ITEMS = 259;
    const uint ERROR_ELEMENT_NOT_FOUND = 1168;

    static DEVPROPKEY DEVPKEY_Device_DeviceDesc;
    static DEVPROPKEY DEVPKEY_Device_HardwareIds;

    [StructLayout(LayoutKind.Sequential)]
    struct SP_CLASSINSTALL_HEADER
    {
        public UInt32 cbSize;
        public UInt32 InstallFunction;
    }

    [StructLayout(LayoutKind.Sequential)]
    struct SP_PROPCHANGE_PARAMS
    {
        public SP_CLASSINSTALL_HEADER ClassInstallHeader;
        public UInt32 StateChange;
        public UInt32 Scope;
        public UInt32 HwProfile;
    }

    [StructLayout(LayoutKind.Sequential)]
    struct SP_DEVINFO_DATA
    {
        public UInt32 cbSize;
        public Guid classGuid;
        public UInt32 devInst;
        public IntPtr reserved;     // CHANGE #1 - was UInt32
    }

    [StructLayout(LayoutKind.Sequential)]
    struct DEVPROPKEY
    {
        public Guid fmtid;
        public UInt32 pid;
    }

    [DllImport("setupapi.dll", SetLastError = true)]
    static extern IntPtr SetupDiGetClassDevsW(
        [In] ref Guid ClassGuid,
        [MarshalAs(UnmanagedType.LPWStr)]
string Enumerator,
        IntPtr parent,
        UInt32 flags);

    [DllImport("setupapi.dll", SetLastError = true)]
    static extern bool SetupDiDestroyDeviceInfoList(IntPtr handle);

    [DllImport("setupapi.dll", SetLastError = true)]
    static extern bool SetupDiEnumDeviceInfo(IntPtr deviceInfoSet,
        UInt32 memberIndex,
        [Out] out SP_DEVINFO_DATA deviceInfoData);

    [DllImport("setupapi.dll", SetLastError = true)]
    static extern bool SetupDiSetClassInstallParams(
        IntPtr deviceInfoSet,
        [In] ref SP_DEVINFO_DATA deviceInfoData,
        [In] ref SP_PROPCHANGE_PARAMS classInstallParams,
        UInt32 ClassInstallParamsSize);

    [DllImport("setupapi.dll", SetLastError = true)]
    static extern bool SetupDiChangeState(
        IntPtr deviceInfoSet,
        [In] ref SP_DEVINFO_DATA deviceInfoData);

    [DllImport("setupapi.dll", SetLastError = true)]
    static extern bool SetupDiGetDevicePropertyW(
            IntPtr deviceInfoSet,
            [In] ref SP_DEVINFO_DATA DeviceInfoData,
            [In] ref DEVPROPKEY propertyKey,
            [Out] out UInt32 propertyType,
            IntPtr propertyBuffer,
            UInt32 propertyBufferSize,
            out UInt32 requiredSize,
            UInt32 flags);

    [DllImport("setupapi.dll", SetLastError = true)]
    static extern bool SetupDiGetDeviceRegistryPropertyW(
      IntPtr DeviceInfoSet,
      [In] ref SP_DEVINFO_DATA  DeviceInfoData,
      UInt32 Property,
      [Out] out UInt32  PropertyRegDataType,
      IntPtr PropertyBuffer,
      UInt32 PropertyBufferSize,
      [In,Out] ref UInt32 RequiredSize
    );

    static DisableHardware()
    {
        DisableHardware.DEVPKEY_Device_DeviceDesc = new DEVPROPKEY();
        DEVPKEY_Device_DeviceDesc.fmtid = new Guid(
                0xa45c254e, 0xdf1c, 0x4efd, 0x80, 0x20, 0x67,
                0xd1, 0x46, 0xa8, 0x50, 0xe0);
        DEVPKEY_Device_DeviceDesc.pid = 2;

        DEVPKEY_Device_HardwareIds = new DEVPROPKEY();
        DEVPKEY_Device_HardwareIds.fmtid = new Guid(
            0xa45c254e, 0xdf1c, 0x4efd, 0x80, 0x20, 0x67,
            0xd1, 0x46, 0xa8, 0x50, 0xe0);
        DEVPKEY_Device_HardwareIds.pid = 3;
    }




    public static void DisableDevice(Func<string, bool> filter, bool disable = true)
    {
        IntPtr info = IntPtr.Zero;
        Guid NullGuid = Guid.Empty;
        try
        {
            info = SetupDiGetClassDevsW(
                ref NullGuid,
                null,
                IntPtr.Zero,
                DIGCF_ALLCLASSES);
            CheckError("SetupDiGetClassDevs");

            SP_DEVINFO_DATA devdata = new SP_DEVINFO_DATA();
            devdata.cbSize = (UInt32)Marshal.SizeOf(devdata);

            // Get first device matching device criterion.
            for (uint i = 0; ; i++)
            {
                SetupDiEnumDeviceInfo(info,
                    i,
                    out devdata);
                // if no items match filter, throw
                if (Marshal.GetLastWin32Error() == ERROR_NO_MORE_ITEMS)
                    CheckError("No device found matching filter.", 0xcffff);
                CheckError("SetupDiEnumDeviceInfo");

                string devicepath = GetStringPropertyForDevice(info,
                                           devdata, 1); // SPDRP_HARDWAREID

                // Uncomment to print name/path
                //Console.WriteLine(GetStringPropertyForDevice(info,
                //                         devdata, DEVPKEY_Device_DeviceDesc));
                //Console.WriteLine("   {0}", devicepath);
                if (devicepath != null && filter(devicepath)) break;

            }

            SP_CLASSINSTALL_HEADER header = new SP_CLASSINSTALL_HEADER();
            header.cbSize = (UInt32)Marshal.SizeOf(header);
            header.InstallFunction = DIF_PROPERTYCHANGE;

            SP_PROPCHANGE_PARAMS propchangeparams = new SP_PROPCHANGE_PARAMS();
            propchangeparams.ClassInstallHeader = header;
            propchangeparams.StateChange = disable ? DICS_DISABLE : DICS_ENABLE;
            propchangeparams.Scope = DICS_FLAG_GLOBAL;
            propchangeparams.HwProfile = 0;

            SetupDiSetClassInstallParams(info,
                ref devdata,
                ref propchangeparams,
                (UInt32)Marshal.SizeOf(propchangeparams));
            CheckError("SetupDiSetClassInstallParams");

            SetupDiChangeState(
                info,
                ref devdata);
            CheckError("SetupDiChangeState");
        }
        finally
        {
            if (info != IntPtr.Zero)
                SetupDiDestroyDeviceInfoList(info);
        }
    }
    private static void CheckError(string message, int lasterror = -1)
    {

        int code = lasterror == -1 ? Marshal.GetLastWin32Error() : lasterror;
        if (code != 0)
            throw new ApplicationException(
                String.Format("Error disabling hardware device (Code {0}): {1}",
                    code, message));
    }

    private static string GetStringPropertyForDevice(IntPtr info, SP_DEVINFO_DATA devdata,
        uint propId)
    {
        uint proptype, outsize;
        IntPtr buffer = IntPtr.Zero;
        try
        {
            uint buflen = 512;
            buffer = Marshal.AllocHGlobal((int)buflen);
            outsize=0;
            // CHANGE #2 - Use this instead of SetupDiGetDeviceProperty 
            SetupDiGetDeviceRegistryPropertyW(
                info,
                ref devdata,
                propId,
                out proptype,
                buffer,
                buflen,
                ref outsize);
            byte[] lbuffer = new byte[outsize];
            Marshal.Copy(buffer, lbuffer, 0, (int)outsize);
            int errcode = Marshal.GetLastWin32Error();
            if (errcode == ERROR_INVALID_DATA) return null;
            CheckError("SetupDiGetDeviceProperty", errcode);
            return Encoding.Unicode.GetString(lbuffer);
        }
        finally
        {
            if (buffer != IntPtr.Zero)
                Marshal.FreeHGlobal(buffer);
        }
    }

}

It can be done using P/Invoke methods on the Windows Setup API. The API functions have been in Windows since W2K. The API calls may require administrative rights. Below is some rough code for using these APIs to disable (as well as enable) devices in C#, which allow invoking:

  DisableDevice(
        n => n.ToUpperInvariant().Contains("VID_3F20&PID_8A1D"),
        true); // true disables the device, false enables it

The first parameter is a filter that is passed the hardware ID. This disables or enables the first device matching the provided filter. There is no effect if the device is already in the target state.

The code follows.

public static class DisableHardware {
const uint DIF_PROPERTYCHANGE = 0x12;
const uint DICS_ENABLE = 1;
const uint DICS_DISABLE = 2;  // disable device
const uint DICS_FLAG_GLOBAL = 1; // not profile-specific
const uint DIGCF_ALLCLASSES = 4;
const uint DIGCF_PRESENT = 2;
const uint ERROR_NO_MORE_ITEMS = 259;
const uint ERROR_ELEMENT_NOT_FOUND = 1168;

static DEVPROPKEY DEVPKEY_Device_DeviceDesc;
static DEVPROPKEY DEVPKEY_Device_HardwareIds;

[StructLayout(LayoutKind.Sequential)]
struct SP_CLASSINSTALL_HEADER
{
    public UInt32 cbSize;
    public UInt32 InstallFunction;
}

[StructLayout(LayoutKind.Sequential)]
struct SP_PROPCHANGE_PARAMS
{
    public SP_CLASSINSTALL_HEADER ClassInstallHeader;
    public UInt32 StateChange;
    public UInt32 Scope;
    public UInt32 HwProfile;
}

[StructLayout(LayoutKind.Sequential)]
struct SP_DEVINFO_DATA
{
    public UInt32 cbSize;
    public Guid classGuid;
    public UInt32 devInst;
    public UInt32 reserved;
}

[StructLayout(LayoutKind.Sequential)]
struct DEVPROPKEY
{
    public Guid fmtid;
    public UInt32 pid;
}

[DllImport("setupapi.dll", SetLastError = true)]
static extern IntPtr SetupDiGetClassDevsW(
    [In] ref Guid ClassGuid,
    [MarshalAs(UnmanagedType.LPWStr)]
    string Enumerator,
    IntPtr parent,
    UInt32 flags);

[DllImport("setupapi.dll", SetLastError = true)]
static extern bool SetupDiDestroyDeviceInfoList(IntPtr handle);

[DllImport("setupapi.dll", SetLastError = true)]
static extern bool SetupDiEnumDeviceInfo(IntPtr deviceInfoSet,
    UInt32 memberIndex,
    [Out] out SP_DEVINFO_DATA deviceInfoData);

[DllImport("setupapi.dll", SetLastError = true)]
static extern bool SetupDiSetClassInstallParams(
    IntPtr deviceInfoSet,
    [In] ref SP_DEVINFO_DATA deviceInfoData,
    [In] ref SP_PROPCHANGE_PARAMS classInstallParams,
    UInt32 ClassInstallParamsSize);

[DllImport("setupapi.dll", SetLastError = true)]
static extern bool SetupDiChangeState(
    IntPtr deviceInfoSet,
    [In] ref SP_DEVINFO_DATA deviceInfoData);

[DllImport("setupapi.dll", SetLastError = true)]
static extern bool SetupDiGetDevicePropertyW(
        IntPtr deviceInfoSet,
        [In] ref SP_DEVINFO_DATA DeviceInfoData,
        [In] ref DEVPROPKEY propertyKey,
        [Out] out UInt32 propertyType,
        IntPtr propertyBuffer,
        UInt32 propertyBufferSize,
        out UInt32 requiredSize,
        UInt32 flags);

static DisableHardware()
{
    DisableHardware.DEVPKEY_Device_DeviceDesc = new DEVPROPKEY();
    DEVPKEY_Device_DeviceDesc.fmtid = new Guid(
            0xa45c254e, 0xdf1c, 0x4efd, 0x80, 0x20, 0x67,
            0xd1, 0x46, 0xa8, 0x50, 0xe0);
    DEVPKEY_Device_DeviceDesc.pid = 2;

    DEVPKEY_Device_HardwareIds = new DEVPROPKEY();
    DEVPKEY_Device_HardwareIds.fmtid = new Guid(
        0xa45c254e, 0xdf1c, 0x4efd, 0x80, 0x20, 0x67,
        0xd1, 0x46, 0xa8, 0x50, 0xe0);
    DEVPKEY_Device_HardwareIds.pid = 3;
}




public static void DisableDevice(Func<string, bool> filter, bool disable = true)
{
    IntPtr info = IntPtr.Zero;
    Guid NullGuid = Guid.Empty;
    try
    {
        info = SetupDiGetClassDevsW(
            ref NullGuid,
            null,
            IntPtr.Zero,
            DIGCF_ALLCLASSES);
        CheckError("SetupDiGetClassDevs");

        SP_DEVINFO_DATA devdata = new SP_DEVINFO_DATA();
        devdata.cbSize = (UInt32)Marshal.SizeOf(devdata);

        // Get first device matching device criterion.
        for (uint i = 0; ; i++)
        {
            SetupDiEnumDeviceInfo(info,
                i,
                out devdata);
            // if no items match filter, throw
            if (Marshal.GetLastWin32Error() == ERROR_NO_MORE_ITEMS)
                CheckError("No device found matching filter.", 0xcffff);
            CheckError("SetupDiEnumDeviceInfo");

            string devicepath = GetStringPropertyForDevice(info,
                                       devdata, DEVPKEY_Device_HardwareIds);
            // Uncomment to print name/path
            //Console.WriteLine(GetStringPropertyForDevice(info,
            //                         devdata, DEVPKEY_Device_DeviceDesc));
            //Console.WriteLine("   {0}", devicepath);
            if (devicepath != null && filter(devicepath)) break;

        }

        SP_CLASSINSTALL_HEADER header = new SP_CLASSINSTALL_HEADER();
        header.cbSize = (UInt32)Marshal.SizeOf(header);
        header.InstallFunction = DIF_PROPERTYCHANGE;

        SP_PROPCHANGE_PARAMS propchangeparams = new SP_PROPCHANGE_PARAMS();
        propchangeparams.ClassInstallHeader = header;
        propchangeparams.StateChange = disable ? DICS_DISABLE : DICS_ENABLE;
        propchangeparams.Scope = DICS_FLAG_GLOBAL;
        propchangeparams.HwProfile = 0;

        SetupDiSetClassInstallParams(info,
            ref devdata,
            ref propchangeparams,
            (UInt32)Marshal.SizeOf(propchangeparams));
        CheckError("SetupDiSetClassInstallParams");

        SetupDiChangeState(
            info,
            ref devdata);
        CheckError("SetupDiChangeState");
    }
    finally
    {
        if (info != IntPtr.Zero)
            SetupDiDestroyDeviceInfoList(info);
    }
}
private static void CheckError(string message, int lasterror = -1)
{

    int code = lasterror == -1 ? Marshal.GetLastWin32Error() : lasterror;
    if (code != 0)
        throw new ApplicationException(
            String.Format("Error disabling hardware device (Code {0}): {1}",
                code, message));
}

private static string GetStringPropertyForDevice(IntPtr info, SP_DEVINFO_DATA devdata,
    DEVPROPKEY key)
{
    uint proptype, outsize;
    IntPtr buffer = IntPtr.Zero;
    try
    {
        uint buflen = 512;
        buffer = Marshal.AllocHGlobal((int)buflen);
        SetupDiGetDevicePropertyW(
            info,
            ref devdata,
            ref key,
            out proptype,
            buffer,
            buflen,
            out outsize,
            0);
        byte[] lbuffer = new byte[outsize];
        Marshal.Copy(buffer, lbuffer, 0, (int)outsize);
        int errcode = Marshal.GetLastWin32Error();
        if (errcode == ERROR_ELEMENT_NOT_FOUND) return null;
        CheckError("SetupDiGetDeviceProperty", errcode);
        return Encoding.Unicode.GetString(lbuffer);
    }
    finally
    {
        if (buffer != IntPtr.Zero)
            Marshal.FreeHGlobal(buffer);
    }
}
}