The two XP Pro and Home options in the boot selection screen must be remnant information in the Boot.ini file from a former dual boot installation... this leads me to believe the cause of it not booting in the first place may have been a misscofigured boot.ini. This would depend on which HD or partition the present XP was originally on... if it was on a second hard drive; rdisk(1)partition(1) or on a second partition; rdisk(0)partition(2), So removing the other XP may have altered the normal Boot.ini configuration so it wasn't able to boot.
Since you now have a clean insalled XP and are now having different problems, the problem must be the digital HD cable... Reason I draw this conclusion: One of my PCs was getting the missing ntoskernel message and also the ntldr missing message... repairing from the Recovery Console didn't help while it should, so with the Hirens Boot CD I confirmed that both files were right where they were supposed to be... so I knew the missing ntoskernel message was false, so it had to be something else... I was getting different booting messages, so I figured it had to be hardware; Replaced the IDE digital cable, and problem solved.