Segunda línea de defensa: Clamwin (gratuito), MCAfee Viru Scan 7, Panda Platinum, NOD32.
Anti Spyware: 
AVG Antispyware, Lavasoft Adaware SE, Steaganos Antispyware, http://www.forospyware.com/
Limpiar basurilla: CCleaner – Más información
Antitroyanos: The Cleaner.
Navegador: Mozilla Firefox
Corta Fuegos: 
Sygate Personal Firewall – Kerio Personal Firewall
Recomiendo visitar: http://www.filehippo.com/
AVG and Avast! are excellent free products that will meet the needs of most users. However neither can be considered to be the best available. That title belongs to commercial products like NOD32, F-Secure, the full version of Kaspersky AV and others. They are however capable packages and offers the financially challenged a real alternative to the major anti-virus suites.
However if you use these free products in conjunction with a free on-demand scanner, you can achieve a level of detection approaching that of the best commercial products. Further improvement is possible by creating a layered defense using additional free security products such as AVG Anti-Spyware (formerly Ewido).