The desktop background turned black, almost all the icons on his desktop disappeared, and everything in the internal hard drive seems to have been wiped out. Since it's his business computer, I was mainly concerned with recovering those files. A Windows Repair window would open and detected several problems with the computer. Several Hard Disk Failure warnings and some delayed write warnings would pop up.
I rebooted the computer several times, and the same thing happened. Windows Repair was unable to fix any of the problems. I rebooted and started the computer in Safe Mode but all the files were still missing. So then, I did a Windows Recovery and recovered the computer back to a previous date (6-16-11, to be exact).
Now the warnings aren't coming up and the background of the computer is back to normal, but all the icons that originally disappeared are still gone and the internal hard drive is still completely empty. Thankfully, I just realized that we have an external hard drive that has been backing up all his files every night so everything is fine. The computer seems to be functioning well but I just want to make sure I don't need to replace some of the hardware or something...
Let me know if you need any more information to help!