Hey there --

I spent a couple of hours searching for a solution when I could not get my Xbox 360 Wireless Controller Receiver to function in Windows 8 Pro x64. I finally figured it out after following a post in the 7 forum. Even then, I had to kind of make it up as I went along. I thought I'd share what worked in case someone else comes along like I did and needs help.

I plugged in the receiver, the led lit up showing that it was connected, but Windows 8 would not install any device drivers. It simply said it was an Unknown Device and that it could not find drivers. Once I found the helpful post in the other forum, I did this:

Right click on Computer, click properties, click Device Manager
Go down to where it shows the USB Connections and right click on the Unknown Device
Select Properties, and in the little window that pops up, select the Driver Tab and click Update Driver
Select Browse my computer for driver software, then Let me pick from a list of device drivers on my computer.
After you click Next, a list of different peripherals will pop up -- scroll ALL THE WAY TO THE BOTTOM and you should see an entry that says Xbox 360 Peripherals. Select that and click Next.
The last driver in the list is Xbox 360 wireless Receiver for Windows Version: 6.2.9200.16384 [7/25/2012]
Select it and click Next, then click yes when the driver warning box pops up. The driver should install, and you should get a box that says Windows has successfully updated your driver software.
Close the window and turn on your wireless controller.
Press the sync button on the receiver, then on the controller. It should sync right up, and if you press the Home button (Big silver button with funky green X embedded in it) A small popup should come up on your screen showing you the quadrant your controller is connected to, your battery status, and Click for Help.

All done!