Do you have any removable media drives attached to your computer? Zip drive, flash memory reader, something like that?

XP likes that kind of removable media to be last. After the DVD/CD drives and everything. I used to get an error message that said something like qttask.exe - No Disk There is no disk in the drive. Please insert a disk into driveDeviceHarddisk1DR1

I thought it was because of QuickTime, because qttask.exe is a Quicktime file, but it turns out it's a Windows thing. I forced my Zip drive to be Drive Z (instead of Drive L), and the error went away.

And the problem started for me when I tried to remove Quicktime, too.