Repair Windows XP installation(Please help)


I have a situation where i have to repair Windows XP installation but i am not able to do so. I have a dual boot setup with Easy BCD (Windows Vista and Windows XP). Since last week for some reason i am not able to choose Windows XP(i am thinking its because i deleted couple of files in system 32 folder that were effected by virus) as soon as i choose XP the system gets rebooted and goes back to the Choice where i have to select either VISTA or XP. So now i can only choose Windows Vista. When i insert a windows XP CD and then boot from the CD, it runs until it loads the files and then does not detect any Windows XP installation at the end.

Can you please guide me in the right direction where i can re-install/repair windows xp over the top of my Current XP installation to fix the problem.

My current setup:

Windows Vista on C :
Windows XP on D:
Thank you kairozamorro for your input but the real problem is that when i insert the Windows XP CD and boot from it then it does not detect my Windows XP installation at all and may be it is still looking at Vista installation which i am not sure at this point.
Maybe the filesystem has been corrupted?

Can you view the contents of the XP drive from inside Vista?