I remember this annoying popup. I'm sorry I don't remember all the details for how I removed it. But I do remember some of my analysis and tools I used to remove. Here you go:
I found that a unfriendly program automatically reinstalled a exe file with a randomized name - that is why reviewing running programs and deleting unknow ones does not work. I believe that it was installed on my computer when one of my kids downloaded a free gambling game
I found and used some of the items others have mentioned in your email stream and they are good recommendations. Another tool I would recommend you download is a tool called "Starter" from Codestuff. Here is a link for the download:
http://www.softpile.com/Utilities/Sy...078_index.html
This tool allows you to view all the programs that auto-startup, see where they are initially loaded and either delete them or disable them temporarily. There is also a nice feature that allows you to look at properties of the file and see ownership when doing analysis of all the junk auto-starting on your PC. It has another window that allows you to view all the programs actively running much like task manager but with much more detail and control.
Best of luck going forward!