My computer has a trojan horse?

I have a trojan horse on my computer and I'm trying to get rid of it. It's not really messing anything up or slowing anything down though. The only problem is that it keeps trying to get me to download "get rid of spyware" stuff that is actually spyware itself. I have spysweeper and am running it for the 3rd time trying to get rid of it. Oh yeah one more problem. It wont let me access Yahoo directly. Like i have to go to yahoomail.com to access my mail and then use a link to get on Answers. weird huh? i also have a Norton Anti Virus Protection program that has destroyed some viruses today but anyway...how do i make my computer go back to the way it was pre virus?

My computer has a trojan horse?antispyware

Is the advertising that it is try to sell you one of these useless products? It is scam advertising trying to swindle you. A computer infection called smitfraud is causing the phony warnings (see below).

AdwarePunisher

AdwareSheriff,

AlphaCleaner,

Antispyware Soldier,

AntiVermins,

AntivirusGolden,

AVGold,

BraveSentry,

MalwareWipe,

PestCapture,

PestTrap,

PSGuard,

quicknavigate.com,

Security iGuard,

Smitfraud,

SpyAxe

SpyFalcon,

SpyGuard

SpyHeal,

SpySheriff,

Spyware Vanisher,