Does anybody know a good free antivirus?

Hi, I need a really good antivirus for my computer, but of course as many students I cannot afford a license for norton or something like that. Does anybody know a free really good one and where can I find it? I have winXP. and also, do I have to unistall my old norton to install the new one?

Does anybody know a good free antivirus?norton internet security 2008

avast or avg both very good and update daily

Does anybody know a good free antivirus?spyware removal

aol's new antivirus is very good .

and safe 360 is very good too.
http://www.zonelabs.com/ (firewall)

http://www.lavasoft.com/ (ad-aware)

http://www.safer-networking.org/ (spybot s%26d)

http://free.grisoft.com/freeweb.php/doc/... (avg Anti-Virus)

http://www.filehippo.com/download_cclean... (Crap Cleaner)

http://www.download.com/ (A useful site for just about anything %26 everything else)
avast.com

then get zone alarm for your firewall
avg free edition

www.download.com/AVG-Anti-Virus-Free-E...

yes u need to uninstall the norton to install avg
Yes, you will have to uninstall Norton as running 2 different anti-virus software could cause problems. I use AOL active virus scan, but AVG anti-virus also gets good reviews. Both offer real time protection and auto update frequently.