If you want a good free anti-virus, then I reccomend Avast Home Edition, which is free as long as you register with them (a simple process).
Avast is easy to use, has a simple interface, a good virus database updater, and constantly scans your computer with it's resident shield, providing protection even for software such as Windows Live Messenger, AIM and Limewire.
Beat free anti-virus i've found around.
Avast anti-virus software : avast.com
Also, if your planning to get an anti-virus, i suggest you might want to get a good firewall too. I currently use comodo, a really good free firewall, that although touchy at times, displaying just about everything as a threat (including windows proccesses that are completely legitamised), but eventually it'll grow to allow these. If you plan to start using it, remember to let through any program you know is installed on your computer, and to tick the "remember this next time" box, so that next time it will automatically give that program access.
Comodo Firewall software: http://www.personalfirewall.comodo.com/
For an anti-spyware solution, the best i've found is Spybot: Search and Destroy, which about on par with AVG Anti-Spyware, also free. Spybot is good, as it has a very large malware and spyware database, and scans in a reasonably small amount of time. It contains an internet explorer scanner, which automatically scans IE while you're using it, and an advanced menu view hich gives you a lot of options about your computer, scanning, and etc.
Remember to always update your anti-virus software and anti-spyware software to ensure they work well!