CCleaner is the standard.

quick speedup tips:
use google chrome - i've been using it since it came out
use ccleaner regularly(i use it like once a week)
auslogics disk defrag(free version, will take a long time the first time, after that run it whenever you install something thats huge like a new game or something)
revo uninstaller free(for crapware, stuff you don't need or use)
AVG 2014 free - covers the most basic stuff- which would be about 90% of users


I avoid c-net like the plague. often they use a proprietary installer that you don't really need. you can get just about everything from that site directly from the source company/product.


I do this for a living and hate seeing people get screwed out of their hard earned dollars by companies like geek squad for simple fixes.

well I should say used too, I design and build websites now.

edit:
links
auslogics disk defrag

revo uninstaller

avg 2014 free