While on the internet I now get a "system alert" message to download antispyware. how do i

system alert: "your computer has been infected by unknown trojan. it's dangerous for your system (critical files can be lost) click ok to downloan the antispyware program to clean your system (recommended)

I have two antivirus programs (symantec and at%26t) that has not been able to remove it.

While on the internet I now get a "system alert" message to download antispyware. how do i remove it?adware

Phony alert boxes or "balloon" pop-ups from the tray (by the clock) about a trojan, virus or spyware infection and the attempt to sell you some useless software to "fix" the problem usually indicates that your computer has a Smitfraud infection. DO NOT BUY THE PRODUCT THEY TRY TO SELL YOU! IT IS SCAM.

Sounds like your computer may have a variant of this ubiquitous Smitfraud infection. Almost all "general purpose","all-in one" spyware and virus removal programs such as AVG, Norton, or Spybot S %26 D cannot remove it compleatly.

Free specialised Smitfraud removal tool is here (SmitfraudFix)

http://siri.urz.free.fr/Fix/SmitfraudFix...

After running SmitfraudFix, to clean-up any remaining infection traces, scan for trojans, adware, cookies, and spyware and remove (free online scan, no downloaded program) with Ewido Online Scanner ( now known as AVG Anti-Spyware). This is NOT the same as AVG Anti-Virus. Press "Scan your computer now online and clean it for free!" on the left.