I run Trend Micro every once in a while. It's free and will delete off any trojans and virsus'.

http://housecall.trendmicro.com/

I also use Norton, but some sneak past it and Trend Micro takes care of them.

For spyware I use Adaware and Spybot.

And finally, use Firefix instead of Internet Explorer. I've been using it for about 2 months and it rocks!

Get it here:
http://www.mozilla.org/products/firefox/