My USB keyboard randomly stopped working in Windows XP. Really randomly. I don't remember changing anything in the past week; I only boot to Windows to play a game and then immediately reboot to Linux, so I don't even use Windows for anything. But when I boot to Windows my USB keyboard lights up the NumLock light and then freezes. No keys work. Plugging in a PS/2 keyboard works. The USB keyboard works fine in Linux and in the grub boot menu. But not in Windows. Unplugging and replugging the USB keyboard doesn't work. Booting without the USB keyboard plugged in and then plugging it in doesn't work.
So, it's an easy fix. I just went to a command prompt in Windows and typed
dmesg | grep -i usb to see how the kernel was loading the USB drivers. Oh wait, WRONG! I'm forgetting that Windows is a crippled heap of garbage. What I DO get in Windows is, after right-clicking My Computer, selecting Properties, and finding the Device Manager, are about 8 lines saying "Human Interface Device" with a little yellow circle containing a white question mark. When you really think about it, that's MORE useful than a printout of kernel messages.
I "fixed" this by using Windows' "Restore Point" crap. I restored back a week randomly and then a magic little progress bar magically filled up and Windows rebooted and magically my keyboard still didn't work, but somehow randomly after 3 minutes it detected it as a new device and then it started working. My pounding the keyboard in frustration like an enraged gorilla may have done something to scare Windows into working, is my theory. Next time I boot I'll give it 90% odds that it does not find my keyboard.
Ever notice how googling for solutions to Windows problems returns about a billion results, none of which are helpful? It's simply not possible to sort through the amount of people who have problems which are NEVER FIXED. Or rather they are fixed in one "easy" step: Reinstall Windows. If anyone asks me for any advice on fixing Windows problems, unless it's something extremely obvious, that is my answer: Reinstall Windows. It's (usually) guaranteed to work, it takes a half hour, and odds are very much against you that you will end up doing anything other than that anyways. May as well get it over with early.