Whats the best free antivirus to deal with trojan horse?

i have been using avast all this while until recently when i contacted a trojan horse virus from a freind's pc. i now noticed that the antivirus files it self have been corrupted by the trojan horse. now my pc is malfunctioning. i have an xp service pack but dont know how to go about formating my pc engineers are over charging me what do i do?

Whats the best free antivirus to deal with trojan horse?kawasaki

ESET is one great tool not to mention my favorite, Bitdefender.

Why I choose both?

Both are excellent as anti-virus and both have firewall which is good against unwanted and anonymous installation or attack especially Bitdefender.

If you need a good anti-virus, make sure it support:

Firewall,Spam and email threats, Block url and etc.

www.bitdefender.com/

www.eset.com/

Ht20

Whats the best free antivirus to deal with trojan horse?nortan antivirus

I have had the same type of Virus in my computer, I bought Norton 360 and it didn't work for me,it didn't delete the virus, but if you would like a free anti virus you can go to:

http://baixaki.ig.com.br/download/AVG-An...

This anti virus in a Brazilian one but it worked really well in my computer, Or if you like you can just pick from these list of antivirus.