- Avast (just to make sure that the downloaded something isn't more than I bargened for! This is an anti-virus scanner by the way, that is free)
- AdAware (and soon, Spybot Search and Destroy because I learned that AdAware doesn't remove EVERYTHING... it misses some stuff)
- Windows Patches (To the person who said they were perfectly fine without any patches, just know that there are viruses that infect you without you doing anything unless you have a firewall. Speaking of which...)
- Zone Alarm (Always looking for a better firewall, but this one serves very nice, for now)
And, when I am at home...
- Smoothwall (an ancient computer turned into a linux based firewall system. Look up Smoothwall in Google for more information. Also, if you are talented with conf files and alike (or mearly in asking questions) you can limit the EXTENSIVE logging so that you don't need a couple gig. hard drive)
I do have some other utilities that I can use if I run into unusual situations (with another person's computer or my own), but luckly I haven't had to use them. They are just a series of emergency boot CDs with every imaginable utility, very handy stuff.
Also, handy when something goes wrong (Visual Studio .net caused Windows XP to crash 2 minutes upon boot after an uninstall (the installer on the HDD was corrupt, I had to use the CD installer after this fiasco)), I use System Restore. It isn't perfect, but it is nice in an emergency.
Other than that, I just keep going on and hoping that everything runs smooth.