CCleaner is a freeware PC optimization tool.
It combines a system cleaner that removes unused and temporary files from your system and also a fully featured registry cleaner!
CCleaner allows Windows to run faster, more efficiently and gives you more hard disk space.
The best part is that it's Small, Fast and Free!

Changelog 

* Complete rebuild in C++
With the requirements for a portable version, 64-bit compatibility and Windows Vista increasing against the limitations of the old architecture. We decided to rebuild the entire CCleaner application in highly optimized C++.
* Faster analyzing and cleaning
Each scanning process was rewritten from scratch and fully optimized. The result being a noticeable speed increase in all areas.
* 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.
* 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 ignore from the cleaning process.
* Loads of little tweaks
Too numerous to mention them all separately, we've tried to improve CCleaner in all areas.