How to Repair the Vista Bootloader
If the bootloader in Vista is damaged, you can repair it by using the installation DVD. But what if your hardware vendor didn't include a Windows DVD with your computer? One of our readers sent a solution. You can find the link to an ISO image (which you can burn to CD or DVD), along with explicit instructions for using it to repair the bootloader, here:
http://neosmart.net/wiki/display/EBCD/Recovering+the+Vista+Bootloader+from+the+DVD