Anti-Spyware Scanners.
Two company's that stand out here are.

Spybot Download
Latest version:
Spybot - Search & Destroy
Protect yourself against spyware 1.5.1

According to PC World and PCMag this is the best anti-spyware scanner and it's free!



AdAware Download
Ad-Aware 2007 Free another quality download. I actually run them both for added protection, as each one can pick up different results. They do not act as an anti-virus you should have software installed for this.









Anti-Virus Scanners
AVG offers a free version.



Firewalls
Comodo Firewall
Free Firewall Software Download from Comodo to protect against Internet attacks with the best Firewall Protection on the Internet. I currently run Comodo and find it an excellent home choice.



Zone Alarm
ZoneAlarm is an easy-to-use firewall that blocks hackers and other unknown threats.