The internal heatsinks and fans have been dusted out? Laptops are not zero maintenance items and the lockups are commonly (for laptops of that vintage) simple overheating issues.
I got a Dell, Latitude c600/c500 laptop, running windows xp pro, with Pentium 3, was slow but working fine...till 3 nites ago and it just locked up...now i'm lucky to get it to completely load. This is what i've tried so far..First was to restore back to a previous date that didn't work keeps getting message it couldn't be restored. I ran a adware scan found nothing, couldn't complete a virus scan it locked up, I was doing these in safe mode. Any suggestions???