Customer's home computer - A Dell Dimension with XP Pro.
Tried to clean out tmp folders for one user, getting "Can't delete temporary files. Access is denied".
Also not possible in safe mode. I removed the drive, connected it via usb to a laptop, and same thing, "access denied".
I'm sure this must be Trojan/Worm activity as I've never seen this in 15 years of doing this for a living.