I recently got around to trying to get my sisters old laptop to start working again but Im having a bit of trouble finding out the problem.

Its a near 4 year old HP Pavilion ZE1115. The specs, as far as I can remember include a 1.1ghz Duron, 20 gig WD HDD [5400 possibly] and 256MB of PC133. She first started having problems with it when she first got it. It would only show half of the full 1.1ghz in the System Properties and always seemed to be sluggishly slow on absolutely everything.

The same applies today.. it takes ages for the thing to boot up and shut down, tasks and active windows become unresponsive for about 5 minutes until they unfreezes and is just plain slow in every way. I reformatted the drive and tried reinstalling Windows XP earlier and the installation just plain stopped and got stuck on 36%, even when those lame "Welcome to Windows" description screens kept cycling over and over and over. I even rebooted and it still got stuck at 36 or 37%. The "CDrom access" light wasnt flashing at all either.

What is the most logical problem here? Possibly a bad hard drive since everything is slow? Bad memory since not more than one thing can happen before the system bogs down? The CPU since it usually only shows ~500mhz in the System Properties window?

Any suggestions are more than welcome...