(Crap)Cleaner has been known as an excellent system cleaner for some time - and it is free. You can try the beta version now.

Ver 2.0 is a complete rebuild in C++ with these features:

# Portable
CCleaner can now run from a USB thumbdrive and be installed/run on a computer without a complicated setup process.
# Compact
The rewrite removed all external file dependencies, so the main EXE is now half the size of the original program and support files.
# Faster analyzing and cleaning
Each scanning process was rewritten from scratch and fully optimized. The result being a noticeable speed increase in all areas.
# Redesigned User Interface
The original CCleaner user interface was looking a little dated, so the GUI was redesigned with a modern look, but without sacrificing speed or usability. New icons were created for the interface and the main program icon was updated with a more modern style.
# Exclusions
It is now possible to specify files, folders and registry keys to ig