What repair feature are you talking about? Vista has various repair options - more than XP did.
But there are other things to try first. For example, have you tried using System Restore to roll the computer back to a date and time before the problem started?
Just one word of warning - System Restore can take an *extremely* long time to launch in Vista. So if you launch it, and nothing appears to happen, be patient.
Wait... and wait... and wait.... Sooner or later (usually later!) it will appear.