It's not that it's a pop up. It's because it's adware. And CHU is supporting it.
Here's what you do, preferably downloading anything on a different computer. DO NOT CLICK ANYTHING ON THAT DIALOG. PRESS CTRL+SHIFT+ESC AND END IEXPLORER'S TASK.
1. Go here: Link
2. Download PCTools Spyware Doctor (will come named as Google Installer).
DO NOT DOWNLOAD THE ONE FROM PCTOOL'S WEBSITE, USE THE LINK ABOVE AS IT IS A DIFFERENT VERSION FROM THE TRIAL
3. Install that on the infected computer and update the definitions through smart update.
4. Do full scans and remove anything it finds. Continue doing this until you receive 0 infections.
5. Restart your computer
6. Do step 4 again.
7. Restart and reset any desktop changes that the virus did.
[Edited by Neo7, 10/9/2008 6:53:32 AM]
[Edited by Vegetta, 10/9/2008 9:16:50 AM]