There is no PC tuning software to my knowledge that works…well technically there are some that will help slower computers but they almost always cause some issue down the road.

http://www.cute-factor.com/images/smilies/onion/87a4e689.gif
As far as software overclocking goes I wouldn’t bother with it. At least not automatic software overclocking. I sometimes use software to overclock my video card but I set the processor and memory speeds myself not let it work automatically as that can cause problems such as screen freezes, artifacts, driver crashes, etc.

CCleaner is what I would recommend for end users that want to clean up temporary files and limit startup items.