some more details would be good - and this may be an XP rather than hard drive problem (I'd suspect so).
So, can you give history on this problem, plus specs for machine please. Also, try safe mode and last known good config and post back results.
If you suspect the hard drive, you could download drive manufacturer's diagnostic utility (most have one on website - and hitachi one - drive fitness - works for most others if you can't find yours).