I'm a computer geek too, and I agree with the good advice people have posted here. I can also recommend
Webroot Spysweeper,
Spybot Search and Destroy , and
Windows Defender (formerly Windows Anti-Spyware Beta, which was formerly GIANT software.)
The latter two are free, and the former is only $29.95. My personal favorite is Spysweeper, but I actually run all three plus virus protection on the computers at my house. Some anti-spyware programs will catch bugs that other's can't, so it's a good idea to run more than one program.
However, even though this will help protect your computer, it will also slow down the load time and take a lot of overhead on your RAM. Iceberg's advice is good; add as much RAM to your computer as you can afford to keep the performance/protection balance in place.
Also, keep in mind that you need to have 1.5x the amount of RAM available on your hard drive in order for the Windows swap files to work correctly. In other words, if you have 1 Gb of RAM on your computer, make sure you have at least 1.5 Gb free on your hard drive, or else your system will run out of virtual memory.