Registry cleaners are programs that eliminate duplicate or undesirable data from the Microsoft Windows Registry.
CCleaner
The CCleaner registry cleaner work on Windows 7 (preliminary), Vista, XP, Server 2008/2003, and older Windows versions like 2000, NT, ME and 98. 64-bit Windows versions are also supported.
If you're set on using an automated tool to fix an issue you have that's caused by a registry problem, I highly recommend you use Piriform's CCleaner freeware registry cleaner tool.
Advanced SystemCare Free
Advanced SystemCare Free from IObit is another excellent free registry cleaner program. Advanced SystemCare Free is very easy to use, has an excellent interface, and includes several other "system care" capabilities, including a registry defrag tool.
Advanced SystemCare Free works in Windows 7, Vista, XP, and 2000. According to IObit, both 32-bit and 64-bit versions of Windows are supported. I tested Advanced SystemCare Free's registry cleaning abilities on Windows Vista 32-bit.
source:
http://pcsupport.about.com/od/toolsofthetrade/tp/free-registry-cleaner-programs.htm
