post beeps but desktop never loads

Hi,
I added a small hard drive of my son’s to my computer as a slave to check it out and it took awhile to boot up to desk top windows xp. It was ok and I shut down and switched to the next hard drive that he was having trouble with and put it in as slave and booted up. I only got past post and the windows before the desk top but the desk top never loads up. I took that hard drive off and now I can’t boot up with my hard drive. I’ve tried putting a cd of win xp in for start up to cd first. and nothing. I tried with norton utilities to try and scan for a virus but it doesn’t go to the cd to read it. the cd -rom shows up in cmos bios. Not sure what else to do.