On one of my windows boxes I was simply unable to use my favorite backlit keyboard. It’s a USB device.
After much frustration – I found that copying this file from another machine fixed it:
C:\Windows\inf> dir usb.inf Directory of C:\Windows\inf 11/20/2010 10:28 PM 42,536 usb.inf
I do a lot of cleaning (and deep cleaning); my bad for clobbering that file.