I noticed the USB ports stopped working, and when I rebooted, sound and networking were dead. I booted with an Ubuntu 10.4 live CD and verified that networking and audio worked (didn't check USB, should have!) so I assume one of the chipset drivers is corrupted? I put the Dell Resource CD in there and tried to install the Chipset drivers and audio drivers but got nowhere.
That suggests a Windows problem - further confirmation would be to try it in safe mode under Windows. If the mouse works, you can either try reloading drivers or bite the bullet and do a system restoration to as-shipped.
Same problem in Safe Mode. This computer came back from a motherboard repair from Dell with a "This copy of Windows is not genuine" error on it. I sent it back AGAIN and they just sent a new, unformatted hard drive. Like that's going to help. We've already completely reinstalled the OS twice.
Could MS be messing with me? I just kept using it because everything worked except for the messages and a black desktop. I didn't have time to deal with this so I just kept using it.