I use to use Registry Cleaners and I found I was running into more operating problems than I had before I used them. Since then I've been told by 2 different computer repair services to stay away from aftermarket (nonWindows) Registry cleaners. I haven't used them for 2 years now and have no issues while my system is quicker than ever in it's 6 year life. I do use 3 different spyware/virus scan programs, each running a scan on a different day of the week. And once a week, I do what was recommended by 1 of the computer repair services and use the Windows Error-Checking program on my systems hard drive that requires a reboot and about 2 hours. To do this, click My Computer/ right click your system hard drive & click Properties/ 1st run Disc Cleanup/ when that's completed click onto Tools and and check Defragmentation (I use a daily monitoring Diskeeper Degrag program so I skip this myself)/ after Defrag is complete Check Now the Error Checking and check off both boxes. A notice will pop up that a reboot is necessary to complete the Error Checking.
Since I've been doing Windows own tools, my system has been running better than ever. And I leave the Registry alone. Because of the length of time it takes to run Error Checking & repair, I do a reboot before I retire for the night (morning actually

) but I always turn off my internet router as my Windows XP is password protected so when I reboot, it doesn't take me straight to my desktop, therefore my firewall hasn't been activated yet. I was told leaving my computer on the Windows password page exposes my system to a connected internet w/o a firewall. That's nice to know,,, so I just reconnect my router before logging onto Windows.
I previously used a handful of Registry cleaners including Registry Mechanic but I can say w/o a doubt that my system has been running much better since I weened myself off these nonWindows programs and put my faith in what Windows provides for their system error checking.
Cheers,
Robin