Note: This review addresses v2.17 of the software.
You may already know the desktop version of CCleaner. Make sure you download the portable version of Piriform's Registry cleaner and repair tool as well. Aside from finding and deleting broken items in the Windows Registry, CCleaner Portable cleans out bits of Internet Explorer that can compromise your privacy (such as the cache and cookies), deletes chkdsk file fragments, manages restore points, and does an assortment of other tasks.
Note: This download link takes you to the vendor's site and automatically downloads the latest version of the software. This program is donationware. It is free to try, but the author accepts and encourages donations towards further development.