It could be a trojan or it might be an adware generating the popup. The likeliest culprit would be a trojan in this case.
You don't say what protection programs you are running. That would be helpful. At the least, you should try running Adaware, Spybot, Ewido and A-squared (all free) in addition to the products you currently use. All of these products are available at Download.com, or find the link to the Anti Parasite suite in this forum. All the links are provided there.
I've scan my computer with all spyware and anti-virus software i know and im still getting that pop-up message in my taskbar telling me that my computer is infected and is I double-click on it its a software called antispywarestrike that opens.
Plz help me im about to throw my computer through the window.