If anyone reading this is using XP and AVG you need to pay attention to this! A recent AVG update gave a false positive for a file called user32.dll in some versions of AVG and it will move the file to the virus vault disabling the file. XP needs this file when starting. Without it, you won't be able to start your computer at all from the hard drive (get out the instillation disk and be ready for a complicated fix if user32.dll was deleted from your XP system):
The Cnet report (link below) says it only affects the Dutch, French, Italian, Portuguese, and Spanish versions of the program. If you've got AVG at all on an XP machine, I'd be wary no matter what version you're running and make sure it's not identifying that file as a virus.
Don't shut down your computer if user32.dll is in your virus vault. You won't be able to restart.
Cnet's report of this:
A WGN radio podcast talking about this: