I believe it is time to use the restore disk or restore partition on the hard drive.
If you can't boot into 'Safe Mode' you can try the BCD boot repair one you enter
the restoration process, but I seriously doubt that it will fix it. Check out he
link for BCD restoration instructions.
http://neosmart.net/wiki/display/EBCD/Recovering+the+Vista+Bootloader+from+the+DVD
If that doesn't work then you will have to completely re-install Vista.