Apple - What is the cheapest way to get windows running on a Mac
If you just need one program, you could try running it using Wine. This is a compatibility layer that allows you to run Windows software on *nix systems, which includes Mac OS X. Here is a tutorial to help you get started.
Note that not every Windows programs will run using Wine - you might need to experiment first. Or head over to the Wine Application Database for user reviews on how well your program is supported.
Alternatively, you could use one of the many virtualization options out there. Parallels Desktop and VMware Fusion are excellent but paid options, while VirtualBox is free (and it works great too). However, you'd need a Windows license to legally run Windows in this way.
Microsoft provides virtual machine disk images to facilitate website testing in multiple versions of IE, regardless of the host operating system. Unfortunately, setting these virtual machines up without Microsoft's VirtualPC can be extremely difficult.
The so-called ievms scripts aim to facilitate that process using VirtualBox on Linux or OS X. With a single command, you can have IE6, IE7, IE8 and IE9 running in separate virtual machines.
Obviously, this tool is aimed at web developers, but if you don’t care about testing in Internet Explorer and you simply need a working Windows VM, you could just install a single VM running Windows Vista + IE9 using this command (after installing VirtualBox, of course):
# enter this in Terminal.app after installing VirtualBox
curl -s https://raw.github.com/xdissent/ievms/master/ievms.sh | IEVMS_VERSIONS="9" bash
A snapshot is automatically taken upon install, allowing rollback to the pristine virtual environment configuration. Anything can go wrong in Windows and rather than having to worry about maintaining a stable VM, you can simply revert to the clean snapshot to reset your VM to the initial state.
The VMs provided by Microsoft will not pass the Windows Genuine Advantage and cannot be activated. Unfortunately for us, that means our VMs will lock us out after 30 days of unactivated use. By reverting to the clean snapshot the countdown to the activation apocalypse is reset, effectively allowing your VM to work indefinitely.
This is effectively a free and legal solution to running a Windows VM on your Mac.
In reply to @josh3736’s comment: here’s an excerpt from http://www.microsoft.com/download/en/details.aspx?id=11575:
Note: You may be required to activate the OS as the product key has been deactivated. This is the expected behavior. The VHDs will not pass genuine validation. Immediately after you start the Windows 7 or Windows Vista images they will request to be activated. You can cancel the request and it will login to the desktop. You can activate up to two “rearms” (type slmgr –rearm at the command prompt) which will extend the trial for another 30 days each time OR simply shutdown the VPC image and discard the changes you’ve made from undo disks to reset the image back to its initial state. By doing either of these methods, you can technically have a base image which never expires although you will never be able to permanently save any changes on these images for longer than 90 days.