Moved this to Malware Discussions for better handling.
It's not really malware in the strictest sense, more of an annoyance really, and no antivirus, no matter what brand, is 100% guaranteed to catch everything anyway.
Scroll down this blog to the part that mentions Windows 8: http://deletemalware.blogspot.ca/2013/01/remove-coupondropdown-pop-ups-uninstall .html
Or use this very reliably sourced uninstallation guide: http://www.bleepingcomputer.com/virus-removal/remove-coupondropdown
Then run Stinger, a fresh copy as it's updated every day, and then perhaps try Malwarebytes Free, linked in my signature below, last line.
To keep Malwarebytes free do NOT accept the free trial offer.
Thank you Peter.
Ex_Brit is right, it's not a virus. One of my clients got this adware/pup after download software from CNET. What a great site it was. Not sure why they are doing this lately.