The owner of the PC (a student) said that it happened one morning when he powered up the machine. As far as I know, this is the same install of Vista that came from the factory (Dell). I'm also not sure about the software (reinstall, new install, uninstall), as all he would tell me was "I powered it on and nothing worked". He's got a few games on there (Halo and a few other regular market games), Office 2007, and AVG antivirus. Other than using the Dell provided backup utility, I don't think he's done anything to the PC. I've done some googling and haven't found anything yet.