Can someone tell me how to REALLY get rid of this virus/spyware/trojan, WHATEVER IT IS?! Please, ple

PLEASE READ ALL THE WAY THROUGH, THANK YOU!!!

When I open the internet, a pop-up says "Your computer was infected by trojan. It's dangerous for your computer, some files can be lost! Click OK to download the antispyware program to clean your system! (Recommended)"

This pops up anytime I click anything. It is not a pop up from Vista, or from my computer. All it says at the top is "Critical Error."

I have updated and ran Spybot, Ad-Aware SE, and a special system check for viruses. It says there are no viruses found on my computer, the spyware/trojans are easily erased, but this pop up still happens. Now it does it over and over when I am online. Does anyone have any advice??

Can someone tell me how to REALLY get rid of this virus/spyware/trojan, WHATEVER IT IS?! Please, please help.?computer security

No antivirus or antispyware protection is perfect, not even the expensive ones but a good mixture will help you clean your system and hopefully keep it clean. It is advisable not to run two or more anti virus applications.

For starters, download, update and run a full scan using the following product:

http://www.superantispyware.com/

SuperAntiSpyware is exceptional and will remove the majority of difficult Trojans and Worms, not just the easy ones.

If possible it is recommended that you load the application in normal mode but run it in Safe Mode. Safe Mode can be started by continually pressing F8 during the boot sequence. However, if you are badly infected you might need to run SuperAntiSpyware more than once to help clean your system. If the only infections now being shown are in System Restore, once you are completely satisfied that you can boot normally, you can either delete the infected restore points manually, or temporarily turn off System Restore.