|Insert a Vista disk and when it gets to the 'install now' screen, click on the 'repair my computer' option, bottom left. Let it go through whatever it wants to do and it will repair the startup in a large percentage of cases. You may need to select the CD as the boot device, if it goes straight to the harddrive - post back if you need more info on changing boot order.|
If you don't have a Vista disk, you can download a 'Vista Repair Disk' - if you do a Google for it you'll find the torrent link - it's all legal, it's just a recovery disk that is sanctioned by Microsoft.
With some computers you can also press whichever key it says to go to the 'boot' menu, and there may be a 'repair my computer' option there.
"I've always been mad, I know I've been mad, like the most of us..." Pink Floyd