Please I need help Trojans?

I need advice for free Antivirus to down load

problem is i have norton antivirus also spy doctor spydoctor says i have trojan popuper 3 infections 6threats 50 infections adware.advertising 3 inf,application tracking cookies 2 inf,trojan.psguard_desktop_highjacker 16 inf

adware.componet.sbsoft19 inf, adware.winfixer 7inf. inf=infection when i run norton virus scan, it says none found or detected! now which one should i believewhen i shut down comp a little while ago it took almost 20 minutes oly had comp for 5 months so i'm a new at this, never had comp course am trying to self learn who evergives me best ans will get 10 points also let me know if i need to delete norton or spywaredoctor or both if i need to download different virus protection also like to mention that spywaredoctor can get rid of these but i have to purchase i think they called it an upgrade I would but can't afford it right now thanks to anyone that can help

Please I need help Trojans?antivirus

This is what I would do, run this 2 scans listed below. They are both free and work good. If it is really there, these 2 programs will find it. After you download them, update them to get the full affect.

Spybot - Search %26 Destroy detects and removes spyware, a relatively new kind of threat not yet covered by common anti-virus applications. Spyware silently tracks your surfing behaviour to create a marketing profile for you that is transmitted without your knowledge to the compilers and sold to advertising companies. If you see new toolbars in your Internet Explorer that you haven't intentionally installed, if your browser crashes inexplicably, or if your home page has been "hijacked" (or changed without your knowledge), your computer is most probably infected with spyware. Even if you don't see the symptoms, your computer may be infected, because more and more spyware is emerging. Spybot-S%26D is free.