That we are dealing with another Memory problem.
First off, does he have Terminators in the open Memory slots?
Second if not, does he have 4 128MB pieces of memory from the same Manufacturer and Class of memory.
Third, change the ordering of the Memory. You be amazed how it'll help finger the bad one... or even solve the problem.
Fourth, if it turns out the Memory is not the problem, look at the Winders drivers for the "High Speed" IDE interfaces. Years ago we started running into problems with Windows 3.1 when the drives started to get to big and fast for it. Sometimes it'd just sit there thrashing. You had to endup enabling some setting... gosh can't rememeber what it was.
Fifth, Are we at SP3 or better on this machine?
Sixth... we might still be seeing the Klez on this machine.