Some little time ago I had a problem with the computer (Core2Quad/2GBRAM/XP) freezing up, sometimes needing a few goes to start up, other times freezing after some time ON. Its only problem was a flat on-board battery, making me set the time/load motherboard default settings regularly.
The only way out of the freeze was to switch off the computer. Of some interest was that in the dozens of times this occurred, I never once had to do a disk drive check.
A-a-anyway, it's had a new battery for about 5 days now and it has not frozen once since.
Am. (And happy now.)