After having all the latest updates for your computer, installing good anti-virus software is the most important thing you can do to keep your computer and identity safe on the internet.

Although there are lots of great commercial security suites that you might be firmiliar with like Microsoft's Windows Live OneCare and Symantec's Norton Anti-Virus there are some very good free alternatives that I find work just as well. My recommendations are listed below:

Avast! 

Avast is the software I use to protect my own computers at home. It does a good job of cutting the line between being lightweight and yet being comprehensive enough to protect your computer against many different routes of infection.

Click here to download Avast! Anti-Virus free edition

Comodo Firewall

Unfortunately, if you are counting on the firewall built into Windows to protect your computer from unauthorized access you will probably be let down. Fortunately, one of the most highly rated firewall solutions is available for free. One of the things that makes Comodo really great is that the developers include a long list of known and trusted applications so you are not constantly being bothered to let a known program have access the internet which ultimately makes the firewall more effective by focusing your attention on the programs that need it.

P.S. if you do use this or any other firewall solution I would recommend you shut off the Windows firewall to prevent any conflicts.