problem with dual boot

First, thanks. This has been a biig help. I've unfortunately run into problem at last step. I've gone through process to rewrite master boot utility and all appeared to go as planned. I got confirmation of file changes as you noted and I'm now able to get screen with choice of OS on start-up. If I choose Vista all is fine. However, if I choose XP receive error as follows:

Windows failed to start. A recent hardware or software change might be the cause. To fix the problem

1. Insert Windows install disc & restart
2. Choose language
3. Click 'repair'

If you do not have the disc, contact system administrator or computer manufacturer for assistance.

File: \ntldr
Status: 0xc000000f
Info: the selected entry could not be loaded because the application is missing or corrupt.

I could of course try to repair or reinstall XP, but worry that doing so will put me back at start and will rewrite master boot utility once again. Help? Any suggestions?