As an IT "guy"  I've come to have a certain toolkit that I trust and use often.  Check out the links below to get the free tools that I often utilize.

Anti-Virus

• AVG Free edition This is the free version of the AVG anti-virus program for Windows or Linux.  This is my standby and the only AV that I run on my personal machine.
• Avast! A good AVG Anti-virus alternative for Windows
• McAfee's Virusscan Online A good online virus scanner by McAffee.  Useful for checking if you have a problem.

Anti-Spyware

• Spybot Search and Destroy One of the best malware removal tools available.
• Ad-Aware Free an oldie but a goodie

Browsers

• Firefox "The Firefox Web Browser is the faster, more secure, and fully customizable way to surf the web."  IE is just plain lame,  time for a real browser that does not put you at risk.
• Opera Another fast and safe alternative to internet explorer

Misc Tools

• CCleaner a great tool to keep your system cleaned up.  I recomend running it at the start of any kind of virus/spyware problem 
• AimFix a good tool to remove all aim associated viruses.

Operating Systems

• Ubuntu Welcome to Linux, leave windowsbehind in the dust(for free!)