Datos de antivirus gratis para Windows XP

2] Which are the best of the free (antivirus) applications and where can I get them?

One of my favorites is AVG Anti-Virus by Grisoft. Their website is www.grisoft.com. As a noncommercial home user, you can download the free version which can be found in AVG Products>>AVG Free Edition. The following link should take you directly to the website of the free version: Free grisoft

I have used AVG numerous times since it was released about 6 yrs ago and it works great. It's detected and prevented (or fixed) a number of virus and Trojan infections on my computer.
Another one I like is Avast antivirus. The site is www.avast.com. Once again there is a free noncommercial version, known as the Home Edition. I have used this software twice over the last 4 years and was fully protected by it. The latest version comes with P2P and IM shields which are important if you file share (usually illegal) and/or chat on instant messengers.

I would also recommend AntiVir Personal Edition which again is free. You should find it at Free AntiVir . I've used this one twice too over the last 4 years and it worked great.

You might find other newer free ones by running a search on Yahoo or Google, but the 3 I've named above have been around for 4-5 years and have done a great job for me.

A good way to test if an antivirus software is working is to do the Eicar Test. Go to http://www.eicar.org/anti_virus_test_file.htm to learn more. Read the instructions before trying it.

Good luck with your antivirus quest. You might want to look into personal firewalls as well as spyware protection while you're at it.