Actually, though it isn't a complete Registry Cleaner, the new Startup Cleaner feature performs the most important portion of this function by helping you reduce the number of applications running on your machine. This has far more effect on the speed of operation of your PC than a few extra entries in the registry, which simply take a few kbytes of space in a file that's typically 20MB or larger.
See this Wiki entry for information about the feature and how it works:
http://channel9.msdn.com/wiki/default.aspx/OneCare.StartupCleaner
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