This is my first post so please excuse my tech knowledge.My son;s computer is running a rather small hard drive (15 gigs) so I decided to replace it with a 40gig hard drive (seagate brand) I re-formatted the drive that went ok. The computer rebooted and prepared to start the window XP install.The Windows logo screen appeared then dissappeared and a blue screen appeared telling me that to prevent damage to the computer it would now shut down.I re-tried the procedure a few more times with the same result.I then installed the same hard drive on my personal computer went through the same formatting procedure and it then proceded to instal windows XP without a problem. I tested the windows install by playing windows games (such as solitaire) opening different screens all without a problem.I then re-installed the drive in my son's computer,it looked like it would start up but it just reverted back to the start up screen over and over.Can any one out there have any ideas. I am using a genunine copy of windows XP.