You can't, and this is why you avoid any and all registry programs. They are snake oil scams, and tend to cause problems, like this one, rather than fix anything. Best case scenario is they don't do anything good or bad.
At this point there's a very real possibility that you're looking at a full OS restore. So, the choice you have is whether or not you will take anything away from this experience, or if you'll just go right back to doing the same things that got you to this point to begin with, because there's little hope for fixing this without some fairly drastic measures either way.
used PC fix regitry cleaner, was asked to restart, now gateway core 2 quad will not startup. Unable to start "Safemode command prompt" hangs after crcdisk.sys. Trying to use F8 Restore point fails with "Transaction support within the specified file system resource manager is not started or was shutdown due to an error. (0x90071A91).
How do I undo the PC FIX process?