DailyBits has a post titled 10 Best, Free Programs to keep Windows Protected.

Windows isn’t secure as you might have known. You’ve probably faced threats and trojans on your computer. There are loads of programs that are targeted at keeping your Windows computer safe from intrusions, here’s a pick of the best of them.

This post covers the essentials which are anti virus, anti spyware, firewalls and cleaners. From the list I have picked CCleaner, a junk remover + registry cleaner + uninstaller, and I like it.