Simple USB mouse install leads to completely unresponsive system!
 

Hi. I'm using XP SP2 and I recently installed a new USB mouse to replace an old one. It worked fine for that session, but the next time I booted, I could get no response from either the new mouse or my keyboard. The keyboard works fine in the BIOS, but neither work in Windows proper. I've tried replacing the new mouse with the old one, and tried pluggin them into every USB port I have-always the same result, no response at all.
I can only assume, for some reason, the driver didn't install properly, because whenever I plug in the new mouse, the PC detects it as new hardware, but of course I have no interaction to tell it to install drivers.
I've tried booting in safe mode, but the system hangs after Mup.sys (which I very much doubt is the problem)-I'm assuming its the attempted driver load after Mup.sys that is causing the issue. With no way to interact with the PC at all, I'm stumped as to how to go about fixing the problem. Help, please!!