faulty hard drive or im not sure?

[k13]

formatted my mates pc, installed xp, realised he had a spear internal hard drive. managed to connect that spear 40gb hard drive dual boot kind of thing. now his pc is having problems like...his pc keeps restarting automatically once in while, internet explorer keeps shutting down, various other thing aswell. when i opened the pc up he didnt have the 2nd hard drive connected to it...do you think that the 2nd hard drive was a faulty one? zone alarm was installed aswell to keep the spywares n viruses out before he went online.

 

[Cromewell]

You say the drive wasn't conneted when you opened it up? Not a bad hard drive then. Random restarts/shutdowns are usually PSU related. Are you sure its not set to automatically reboot on critical errors (blue screens)?