The Apple Wireless Keyboard will work with Windows as long as the Windows computer has Bluetooth capabilities. Technically, no driver is necessary, but if you need to use all the keys such as forward delete, home, end, page up, page down, print screen, Control+Alt+Delete, eject, and media controls, you will need to install the UAWKS file.
For 64-bit Windows users, a link to an alternate driver was provided.
Remember, this is "unofficial" so don't throw away your Windows keyboard so you have a failsafe if something goes wrong.