How can I uninstall K9 Web Protection without K9 admin password?

Manual removal instructions

No third party software required. Tested with K9 Web Protection version 4.4.268 on Windows Vista SP2 (32-bit). Confirmed by @stiemannkj1 to be working on Windows 7. Should also work on Windows 8.x.

1. Create a new text file. Copy and paste the following batch script code, then save:

   @echo off
   
   set keys=^
    "HKLM\SOFTWARE\Blue Coat Systems"^
    "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\k9filter.exe"^
    "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\Blue Coat K9 Web Protection"^
    "HKLM\SYSTEM\CurrentControlSet\Services\bckd"^
    "HKLM\SYSTEM\CurrentControlSet\Services\bckwfs"
   
   REM remove registry keys
   for %%G in (%keys%) do reg delete "%%~G" /f >nul
   
   set folders=^
    "%programfiles%\Blue Coat K9 Web Protection"^
    "%programdata%\Microsoft\Windows\Start Menu\Programs\Blue Coat K9 Web Protection"
   
   REM remove folders
   for %%G in (%folders%) do rd /s /q "%%~G"
   
   set files=^
    "%windir%\System32\drivers\bckd.sys"
   
   REM remove files
   for %%G in (%files%) do del "%%~G"
   
   pause
   exit /b
   

2. Make sure file extensions are shown and rename it to RemoveK9.cmd (or whatever you like, as long as it has the .cmd extension).

3. Restart Windows in Safe Mode.

4. Right-click the .cmd file and select Run as administrator from the context menu. Wait for the batch script to finish.

5. Start regedit.exe and navigate to the following registry key:

   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_BCKD
   

   Right-click the LEGACY_BCKD key and select Permissions from the context menu. Click Advanced and select the Owner tab. Then select Administrators from the owner list, tick the Replace owner on subcontainers and objects option, and then click OK. Then select Everyone and tick the Allow checkbox for the Full Control permission. Click OK, right-click the key and finally choose Delete.

6. Restart Windows.