Maybe this is just me... others seem to be having success with this software.
But after I installed this and ran a full scan, it found over 100 problems (this is a fresh install of Windows, along with Visual Studios and SQL Server Std 2005, as of Friday).
I did not go ahead with the fixes, just closed the program, as it kept saying a bunch of the SQL Server registry entries were wrong (I didn't believe it as it is a fresh install).
Anyway, it totally screwed up my PC - Windows stopped responding, could not launch or open any window, etc. Had to hard reset a few times. Because Registry Mechanic starts up automatically, it made it a bit more difficult to fix. I eventually got the program to not load at startup, then restored the system to before I installed this program.
Now my PC is fine, just like before I installed it.
As the old adage goes... if it ain't broken, don't fix it. IMHO.