Baku allows you to search for system registry errors and unneeded files that can be safelly removed.

Features
Deletes empty folders, 'History' folder contents, 'Recent documents' folder contents, 'Temp' folder contents, temporary internet files, cookies.
Searches Windows log files, shortcuts to missing files and folders and user specified file types.
Registry scan removes unused and obsolete keys, including ActiveX/COM, Application Paths, Fonts, Help files, Icon files, Sound files, Uninstall Programs and Windows Installer.
The registry is automatically backed up before any changes are made.
Implements the Department of Defense clearing and sanitizing standard DOD 5220.22-M, to give you confidence that once deleted, your file data is gone forever.

Limitations: Requires Microsoft .Net framework 2.0 or better.