When you say stopped booting, what exactly happened? Any error messages or any specific screen presentations, like a black screen with a blinking cursor on the upper left?
A startup repair may have to be run 3 times to repair some types of problems.
If it isn't booting and you have the small system partition on the drive, it may not be D: but another letter.
Does the drive show in the Bios during boot, or does it take a long time to get past the bios screen?
If it isn't the hard drive, it might be a controller problem, or something has messed with the boot system.