The windows registry contains a lot of information. Its consistency can be checked with good commercial programs like SymantecΓäó System Works. But there are some small things I miss with those programs. Here is what SpyBot-S&D searches for:

• Missing help files ΓÇô the registry contains information about the location of some help files. If this information points to incorrect directories, Spybot-S&D will inform you about and allow to fix.
  
  
• Missing shared DLLs ΓÇô the registry contains a list of dynamic link libraries, where they are located and how many programs are using them. SpyBot-S&D checks if all locations are correct and allows to change them if not.
  
  
• Application paths ΓÇô some applications (mostly those registered to a file extension) are registered in the registry. If they are pointing to a program file no longer existing, Spybot-S&D can change their path or delete their entry.
  
  
• Wrong Uninstall information ΓÇô every program that has its own uninstall routine stores some information about it in the registry. If this information is incorrect, Spybot-S&D will tell you about. For example, the uninstall program may have been located inside a temp directory (there are lots of programs that stupid!).
  
  
• Broken Desktop Links ΓÇô if one of the links on your desktop links to a file that no longer exists, Spybot-S&D will tell you and allow you to either point the link to another file or delete it.

Warning: Please be aware that changes to these items can corrupt your system! If you are not sure whether a setting is really a problem you┬┤d better leave it alone!
This warning especially applies if you are using Microsoft OfficeΓäó. This software suite has some registry entries pointing to wrong directories and some even pointing to non-existent help files. I have changed the first, but I would not delete the other one, because they may well point to files that will be installed on that "Install on first use" basis.