This looks complicated but it’s not, it’s nice to know how to do a system restore for future use.
I usually make a system restore check point before I download programs or test them on another computer or windows will automatically do a restore point.
http://www.sevenforums.com/tutorials/700-system-restore.html I would stay away from links that say scan your computer fix errors etc.
Also lots of downloads come with google tool bar etc you need to read carefully what you download & uncheck what you don’t need…
When you download programs & uninstall whether it’s antivirus or other programs you always get clutter left. Antivirus programs need uninstall tools from their website, but like other programs can still leave bits behind.
Say I wanted to uninstall Avast I would follow the uninstall instructions, once done would do a search for any left over items then look in the registry just to be sure.
If you need to find anything out about any problem or topic do a search online for it.
Youtube is very useful too, they have every topic & you can watch videos on how to do system restores etc or just watching music video clips.