Trojan Vundo

I have a pop-up that shows itself whenever I open my documents or open internet explorer. But not when I use Firefox. It states:

"Critical System Error
Your Computer Was Infected By Trojan.Vundo
It's Dangerous For Your Computer, Some Files Could Be Lost!

Click OK To Download The Anti Spyware Program To Clean Your System! (Reccomended)
[OK] [Cancel]"

When I Click the "x" Or Cancel, it just goes away for a few seconds and opens again when I click on something, If I Click "ok", a pop-up opens to download "defender-install.exe" "which is a: Application. From: http://iedefender.com"

I tried registry cleaner, spybot s&d, symantec to find any problems and remove them, Norton doesn't come up with anything, nor do any of the other programs that were tried.

Any help on getting rid of whatever this is, is greatly appreciated.

Thanks,
-Jarfark