I'm going to give a little advice here on safe browsing. (I'm assuming you're a windows user)
1. The default login you should use should not have sysadmin privileges.
You need to create a user with minimal rights and absolutely NO RIGHTS to install software.
You NEVER, NEVER, EVER browse with an account which has sysadmin privileges.
If you do this ONE thing, you will wipe out 99.9% of your problems.
2. Switch your browser to Firefox and add the plugin NOSCRIPT. Javascripting is a big security hole.
3. Turn off flash, except for specific sites. Flash is another source.
4. Get a pdf reader without scripting. Adobe added that nasty capability and this is why I don't use it.
5. Get a used router and place your pc behind that (if you're on cable, this is easy). You can easily configure your router to not respond to probes.
6. Never click on links in emails, or on web sites. You should google that link and at least see what google thinks of the site.
7. Don't click on a close box for a popup. Instead, go to your task manager and kill your browser. People will fake close boxes which don't close, but instead attempt to install.
8. Don't take files from strangers. Stop any peer-to-peer sharing, like bit-torrent and the like.
Antivirus? I never use it. It's almost useless. If you do these things you'll be great.
If you want better, then go to vmware's site and download the vmware player and an appliance image and use it to browse. Ever if that player gets infected, it won't matter, because it's sandboxed. Or you could use a bootable linux disk and just like the vmware player/appliance combo, you're golden.