That is odd, I have been using registry mechanic since before vista was released and had no issues what so ever. If you are sure that it was registry mechanic that messed you up you can also try using the restore feature of registry mechanic to restore your registry before the cleaning dude.
a great way to mess your pc up is to use registry repairers and cleaners, most pc's i work on have been messed up with these progs in the wrong hands. but they keep me in business so who am i to complain, 100 bucks a throw is good money.
Hmmm - I have been using CCleaner on my XP install for a long time without issues (great little app). So when I switched to Windows 7, I installed and kept using CCleaner - mostly to clean out the temp files etc and occaisionally I use reg cleaner, which very rarely finds anything wrong. That was until yesterday, when I used CCleaner to check and clean the registry - it found about 4 or 5 issues, which I decided was OK to fix, thankfully saving a registry data back-up first. When I started the computer later in the day - Windows 7 would not load. All I had was a black screen and a mouse pointer. Suspecting my last clean may have been the problem, I was able to boot Windows 7 into Safe mode and restore the last saved CCleaner registry data back-up - and that was it, Windows re-booted fine with no further issues. My lesson from the experience, was in future to be VERY careful using CCleaner to clean the registry - nuff said!
I also use ccleaner. I just want to comment and say I have not had any problems with this program on my Windows 7 Home Premium 32 bit OS. For a free program, it does a better job, than a lot of the retail programs!