Did you try another USB port?
Try the steps located here: http://www.tomshardware.com/answers/...nstalling.html
1. Download Xbox 360 Accessories here
2. Install that, then plug in your controller and wait for it to epically fail.
3. Open Device Manager (devmgmt.msc)
4. Find and double-click the unrecognized driver which is probably called "Controller" under "Other devices"
5. Go to the "Driver" tab and hit "Update Driver". Hit "Browse for driver software". Hit "Let me pick from a list of device drivers on my computer".
6. In the list, open Microsoft Common Controller for Windows Class. Your 360 controller drivers should be in here. You might get a warning, just ignore it.
7. Game it up