Free Stuff
There are *many* things people can take care of with their own PCs for free – even though many companies charge for this (or give you the tools to do it free but charge you to use those tools.
All of the programs below are free to use in an effective manner. You can purchase versions of them for more features, better support etc. but it is not needed. The best part of purchasing them is that you help support these companies.
System Cleaners
CCleaner is a great cleaning program for cleaning all the temporary files, cache, and other types of files that can bog down your PC’s performance. It also has some disc management tools, as well as drive wiping tools (and as far as I know is the only free program that supports the Gutmann method (renamed “Very Complex Overwrite (35 passes)” in CCleaner due to copyright issues).
Malware Programs
Safer-Networking’s Spybot Search & Destroy is free program that will search your computer for spyware and other kinds of malware from your system. Personally I would recommend a good clean (like using CCleaner) before performing a scan because not only will simply cleaning out your cache will get rid of some spyware, it will also eliminate tens to hundreds of thousands of files that the program will need to scan.
Lavasoft’s Ad-Aware is another free program that will search your system for spyware (etc.).
Personally, I would recommend both programs (but don’t use them at the same time – run one, then the other) because there are times when something is picked up by one but not the other. This isn’t because one is inferior or one doesn’t work but it can take time for these companies to catch onto the latest threats.