Viddler

Good stuff.

AVG: http://download.cnet.com/AVG-Anti-Virus/3000-2239_4-10385707.html
Avast: http://download.cnet.com/Avast-Home-Edition/3000-2239_4-10019223.html?tag=mncol
Advanced System Care: http://download.cnet.com/Advanced-SystemCare-Free/3000-2086_4-10407614.html?tag=mncol
Spyware blaster: http://download.cnet.com/SpywareBlaster/3000-8022_4-10196637.html?tag=mncol
Spybot Search and Destroy: http://www.safer-networking.org/en/index.html
Auslogics Disk Defrag: http://download.cnet.com/Auslogics-Disk-Defrag/3000-2094_4-10567503.html
CCleaner: http://download.cnet.com/ccleaner/?tag=mncol
Ad-aware: http://download.cnet.com/Ad-Aware-Anniversary-Edition/3000-8022_4-10045910.html?tag=mncol
Zone Alarm: http://download.cnet.com/ZoneAlarm/3000-10435_4-10039884.html?tag=mncol

And the extras:
Firefox: http://www.mozilla.com/en-US/firefox/personal.html
(link is on the lower-right)
OpenOffice: http://www.openoffice.org/

Another defragger:
http://download.cnet.com/Smart-Defrag/3000-2094_4-10759533.html?tag=mncol;pop

And don't forget to keep your Windows updated:
(this website only works if you visit with Internet Explorer): http://update.microsoft.com/
or http://update.microsoft.com/windowsupdate/v6/default.aspx?ln=en-us

And while you're at it, why not go for an Ubuntu dual-boot?
(it's a free open-source OS, separate from Windows.): http://www.ubuntu.com/
(make sure you install to a separate partition, so you don't delete windows)