How come my computer will not boot if I remove my old primary hard drive?

by on August 16, 2010

Q: My father just added a larger hard drive to his computer at the local computer shop. He had a 40 gig hard drive with Win XP and he had them install a 275 gig in the box too. They backed up all his info or cloned the other drive (not sure which). He now has 2 Win XP operating systems (this was not his intention). One on the 40 gig drive and one on the 275 gig drive. The problem he has is when the computer is started, it boots to the old XP on the 40 gig drive (different desktop and icons). The only way to get it to boot to the new XP on 275 gig drive is to restart (not shut down) the computer. To fix this I reformatted the old drive but now when starting the computer it says that NTLRD is missing and hit Ctrl Alt Del to continue. When I hit Ctrl Alt Del it loads the new XP on the 275 gig drive and all is well. I have checked to make sure the Bios is showing the new drive as primary. I tried to remove the other drive in the bios but computer will not boot at all, says disk error. I am thinking I have a Master Boot Record issue? Any idea how to fix?