The Troubleshooting Shows You Step-by-Step How-to Installing the Needed Driver and Enabling the Apple Wireless Keyboard on Parallels Windows 7 Virtual Machine.
Just Relax & Take the Time of Carefully Reading and Executing the Instructions Contained Here and the Issue Should be Solved.
Download Apple Bluetooth Driver:
Important Thing to know is that when you will Activate the Bluetooth Driver on Paralles your Keyboard will be Unavailable on Mac until that will be Deactivated
So, at the moment using an Apple Wireless Keyboard you will have to Take an Annoying Step of Switching On/Off the Bluetooth on Parallels.
Right click on Bluetooth Icon Task Bar -> Add a Device
Control Panel -> Hardware and Sound -> Add a Bluetooth Device
A Window will Pop Up Looking for your Device
In a Little While your Device should be Recognized…
If your Device isn’t Founded try to Turn it Off/On and wait for a while
If Windows doesn’t find Any Device try to Reboot VM and Repeat Activation
I Hope this will be Enough to Solve your ProbleM :)