A great all round program for helping you to keep your system tidy and running smoothly is a program called CCleaner (crap cleaner!). CCleaner cleans all old, temporary, uneccesary files, log files etc, it will also scan your systems registry and get rid of any problems it detects.
It is also safe to use, as it will ask if you wish to create a back-up before deleting registry entries, so that you may roll back to your previous settings should you need to (although after using it for about two years I have never had to!)
It will also clean up temporary files from many common programs as well as your system files ... such as cookies and internet history from which ever internet browsers you use (good for privacy also). You just check the boxes against the programs you want scanned and cleaned. CCleaner can clean many programs temp files, although it will only show those that it has detected on your computer. Another feature is its ability to clean any directories that you enter manually -- you may have a downloads directory you want cleaned regularly for example.
More info: http://www.lessfuss.co.uk/free-software-system.php#cccleaner
This program is totally FREE to use forever - including updates - and doesn't require any kind of dodgy serial number, or patching to make it work (w810iflashfreak is recommending programs that are NOT free and is actually promoting theft and has been reported).
CCleaner also has another couple of useful tools like a start-up manager, so that you can see what programs start when your system is booted, enabling you to disable any you don't want to start with your PC.
Another tool is the add/remove programs list manager, allowing you to remove entries from this list should Windows not do so when you've uninstalled something.
Highly recommended and very easy to use.