I have a lot of ranting to catch up on. But I just read John Moran's FireFox recommendation, and I had to concur. We'll somehow manage to work it into this Free Computer Security series.
Yes FireFox certainly is free. And it provides security in the same sense that a Volvo provides safety. Driving (or riding in) an automobile is not safe. But if you have to do it, do it in a Volvo. Similarly, browsing the World Wide Web is not safe. But if you have to browse the Web, FireFox is a good choice.
FireFox may not be completely invulnerable to exploits. Just read the FireFox 1.x bulletins at Secunia to see. But at least it's not tightly integrated into the Windows OS as Internet Explorer, the Yugo of browsers, is. That means Spyware is less likely to take root and germinate.
FireFox's ability to suppress unrequested popup windows means you don't need a separate popup blocker program.
Many exploits involve tricking users into thinking they're on a site other than the malicious site they're actually on. So the SpoofStick extension was created to address this. SpoofStick displays the domain name of the website at the top of the browser window in bold, green letters. (The font color and size are configurable.) This makes it easier to tell if you've been redirected.
But remember, the safest computer is one that's not connected to the Internet. If your tolerance for risk is very low, you'll not have a modem or NIC in your box.
On the usability side of things, I happen to prefer FireFox's tabbed browser concept. If you've always used Internet Explorer, tabbed browsing might take some getting used to. Here's how it works. Instead of having one button on the TaskBar for each open web page, there's just one button on the TaskBar for the main browser window. If you have multiple web pages open, you select the one you want by clicking the appropriate tab or cycling through them with Ctrl-Tab. Microsoft Excel can be configured to work this way. Microsoft calls this Multiple Document Interface, or MDI. I call it cool. (Just one thing. To make Ctrl-Tab switch to the most-recently used tab rather than the next tab, install the LastTab extension.)
Give it a try!
 Actually, the safest computer is the one that's never turned on.