[Womble]

Wondering if anyone can help. My brother brought his PC to my house recently because it went on a go slow!. i looked through the process list but couldn't find anything untoward. He was running Zone Alarm and an up-to-date NAV. The machine was un-usable, so I ended up re-imaging it. Today another friend has phoned, and she has the same symptons. The PC boots up ok, but when you go to open a folder the CPU reads 100%?!. I can't re-image hers as it has been supplied by her work, Has anyone any ideas as to what they picked up?, both are running XP.

HELP

PS;thanks inadvance for your time