That file used be critical in identifying the installed versions of Windows, but is no longer existent under Vista as Microsoft moved from the NTLDR and boot.ini to the Windows Boot Manager and BCD store. The only time it should be an issue is when you're dual-booting Vista with a previous version of Windows, and even then only apply if you're trying to boot the previous version. If you would, fill in a few details:
1.) If Vista currently installed, or were you just attempting to repair the problem using the Vista DVD?
2.) Are you dual-booting Vista with a previous version of Windows, such as XP?
3.) If this is strictly a Vista system, did you upgrade from Windows XP?

This is a common problem under XP, but non-existent under Vista unless a previous edition exists on the system, details of which you'll need to fill in.

John