It's rare to find a really good security tool. What's even more rare is finding one that's free. Yet good security tools that cost you nothing do exist. Thanks to ZDNet, you're about to learn about ten of them. If you're running a Windows machine, you need to see this photo gallery. It's a great little roundup of some of the more effective programs available, though it does have its limits. Large corporations are not going to be able to get by on these, nor should small-to-medium sized businesses attempt to survive on freebies. Still, these are additional layers of protection that could save the data on your computer.