Due to being raped by viruses, I went out and bought a new computer. I used my old virus-ridden hard drive in the new computer and cleaned it up with norton anti-virus. I was using it as a back-up drive, but then decided I would like to put it into my old computer and sell it.

So I popped in the recovery disc, selected "full system recovery". Some sort of error happened, so I rebooted, and it said "No OS detected, press 'r' for full system recovery"

So I did, then I keep getting a blue screen saying "Check for viruses. Check HD for proper configuration, Run CHKDSK/F, scan for HD corruption,
Tech info: STOP 0x0000007B (0xF7948640 0xC0000034 0x00000000 0x00000000"

Any ideas?

Did you format the drive? If you did you might have formatted the recovery partition on the drive, If you did, you can order cd's or a dvd from Compaq and that will rebuild the restore partition and the OS. Also Virus could have corrupted the restore partition (assuming you have one)