Windows diagnostics tool

Has anyone any recommendations for a decent free download to scan and repair any errors on my pc. I have downloaded various registry cleaners etc., but they all say "we have found 'x' number of problems but can only fix some unless you purchase the software"

Are there any that actually do the job?

Ccleaner is free try it http://www.ccleaner.com/

system mechanic is pretty good
www.iolo.com
trial version will clean it up for you.
then if you like it you can buy, it's not that expensive
hope that helps

Key Post: helpful links for a clean pc
Free software and tech support links