Is there a good, free antivirus software I can download? I have the Verizon security suite, but I'm quite sure it's not catching everything. Barring that, what's the best way to clean the viral crap off my computer?
Are we talking about a program that runs all the time and tries to catch virii before they get installed, or one that removes them after?
For prevention, Microsoft Security Essentials or Avast seem to be the best free options.
Whatever VZ is using is probably pretty good too. None of them are perfect...paid or free.
For removal I would use more than one scanner to remove virii. Eset.com has a free online scanner. MalwareBytes offers a free scanner that you download and install.
In all post-infection cases, you want to make sure that the scanners are not identifying false-positives. Set them to notify but not clean (or delete or quarantine). That's why we use multiple scanners. If they agree that a file contains a threat, then we quarantine (remove...delete) it.
If you are talking general computer cleaning, CCleaner is good but it will help you remove things that you really didn't want removed. WinDirStat will show you what is taking up all the space on your hard drive.