computer working but not responding(!?)

[mikeh420]

I am working on a friend's PC that had a UNMOUNTABLE_BOOT_VOLUME blue screen. Turns out HDD is bad, waiting for an RMA.

Meanwhile, I loaded a fresh copy of XP w/SP2 on a spare HDD, then loaded some of his apps. Most work fine at first, but after a few minutes, double-clicking on any icon does nothing, also Task Manager doesn't work (CTRL-ALT-DEL). Tried this on a second spare drive, and got the same results.

The CPU is a P3-450MHz, could it be old enough to cause this problem, is it possible the CPU is overheating? (fans are working).

Any ideas would be greatly appreciated.

****just went and checked on the PC, and it has a few instances of explorer, defrag, etc. which I tried to start 6 or 7 min ago.********