A free firewall, it works similar to Norton Internet Security. You need a free antivirus programs (see below) for a complete protection. Download and read reviews from C|Net.
A free antivirus program, just as good and up-to-date as Norton. Currently, this is the perfect free addition to ZoneAlarm firewall. Download and read reviews from C|Net.
3. System Cleaner
"CCleaner is a freeware system optimization and privacy tool. It removes unused files from your system - allowing Windows to run faster and freeing up valuable hard disk space." Download and read reviews from C|Net.
I personally use these programs and I find them very useful. They are free and do not contain any spyware/adware.
40+ Free Windows Apps For You. Technology Bites, 2007.
The ones that I am trying now are Freemind, a free mind-mapping software, and Truecrypt, a free open-source disk encryption software for my external hard drive.
Scan a File Using the Top Antivirus Software. Google Operating System, April 11, 2007.
The Best Free Software for Windows. Digital Inspiration, 12/2007.
Avoid Viruses, Spyware, Adware and Trojan Horses. Information Technology in Medicine, 2008.