Stay away from registry cleaners, they can cause more problems than they are worth.
Have a bit of a read of
Registry cleaner suggestions? - Windows
There are other alternative steps that you can take to improve your PC's Performance.
If you want a good cleaner program use
Windows Cleanup, You will be amazed at how
much junk files it will clear off your PC. It is probably one of the best utilities that I have
come across. (Not a registry cleaner)
Also adding more memory can help to improve the speed of your PC.
Cleaning up Unwanted programs from startup can also reduce the startup time & improve performance.