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#21
ASTSRV.EXE belongs to the software A.S.T Copy Protection or Nalpeiron License Management or Tiffen Dfx v1.0 for Photoshop by Advanced Software Technologies or Nalpeiron Ltd. If you have any of these installed on your machine (either factory installed or something you added) that would explain why you're showing it. If you're not using the associated program you could always uninstall it.
As for registry cleaners, I'd agree with what others have said. Generally speaking, it's best to let Windows 7 take care of the registry. However ...
CCleaner is a reputable free utility with a built in registry cleaner. It's not very aggresive and seems to err on the side of caution. (If it's not sure about a registry entry it does not seem to recommend removal.) It also gives you the opportunity to back up your registry before any cleaning is done so if there are problems you can restore the original registry files.
CCleaner - Optimization and Cleaning - Free Download
Registry - Backup and Restore