I think you mean to say BOOTMGR...
I have seen this problem, but it's been a while since I had to fix it on an XP machine. At work, we just replace grumpy PC's and then re-image the crap ones later.
I think this is how to fix this problem, but again, it's been a while.
Boot from the XP CD and then select the recovery console during setup. Select the version of windows and when you get to a command prompt type:
chkdsk *: /f/r
You use the wildcard because when setup loads, the temp drive is assigned the C letter, so running the chkdsk on C isn't going to do you any good.
While the above usually fixes it, I have run into scenarios where it didn't. In that case, you need to get a hold of a Windows Vista/7 CD. On there, you will find the "bootmgr" file. It will not be found by XP unless it's in all caps. You cannot rename it to all caps without renaming it to something completely different first. So, you have to take the drive and copy the "BOOTMGR" file to it, overwriting the one there and all should be good.