[SOLVED] NTLDR is missing

NTLDR is missing, came up on a computer I use. I must have done something to cause this but I cant figure out what it is but I did the fixntldr.exe to boot the computer with, got nine options and the third one booted the computer up ok but now I have to go through the boot up with the floppy disc every time. There are more things I can do so I can boot up normally but I do not fancy going through the full procedure. Is it possible that I could re-install WinXP and Service Pack 2 if I have to so that it will put the computer right? This computer only has software and hardware plugged into it for certain items and nothing else so if I lost anything I could soon put it back.