Make sure you keep your Windows OS current by visiting Windows update occasionally to download and install any critical updates and service packs. Without these you are leaving the backdoor open. If your computer is fairly new you might want to consider Microsoft Windows 10.
Also download, install and keep updated- Antivirus Software
Free for home users:
avast! Home Edition Download (our favorite free anti-virus)
Online anti-virus from Bit Defender
Many exploits are directed at Internet Explorer, you dont have to use it. Try a different browser.
Like Firefox, or Opera
Download one or two of these, install and update before using:(if these are constantly finding malware, then you need to make changes to your browser and or your habits)
Spybot Search and destroy
Ad-Aware SE Personal edition
Be careful with spyware "removers and scanners"-- there are many programs that "claim to remove" spyware but are nothing more then “Crippled Software” aimed to be Re-branded and Sold.
Like Microsoft Office but its to expensive, try open office. Its free and almost as good !
Watch what you download, and where you download it from. Many programs come bundled with extra software. You may be installing more than you think ! Make sure you understand what it is you will be downloading and installing to your computer. Visit the makers website, learn more about the program. Read the EULA agreement. If you search hard enough you can always find a "clean" alternative to any software. Stay away from warez and crack sites. Be Careful what you download from file sharing networks such as Limewire and Kazaa. If you are not sure, don’t download it.
Here’s a Little tip: Many download sites frequently ask for a email address. Try just making one up or set up a email account such as Hotmail or Yahoo Email just for that purpose. Let that email address get all the tons of advertisements that are sure to follow.