About cleaning the unwanted stuff on ur comp like temporary files and anything else unwanted, then just download a software called CleanUp. You can download the latest version, which is v4, from this link :
http://www.stevengould.org/software/.../download.html . I used this software and in like 200 runs i have deleted more than 2.8GB worth of unwanted stuff.

Also you could download a Registry Cleaner, it cleans up the full registry of wrong or wanted stuff in ur registry that make ur comp slow and which makes system errors. I would suggest buying a Registry Cleaner, because most of the free registry cleaners dont' clean the whole registry, only a few only. Also you can search through the Syschat downloads section on the top of every page for a Registry Cleaner.I hope i was of any help. Good luck.