I would scan your computer with Malware bytes and see what it detects and removes. You can get the free version here if you have never used it:
http://www.malwarebytes.org/products/malwarebytes_free/
Coupon dropdown claims it is "Norton Safe", and it appears to have an official site. This is what the site says to do to uninstall:
http://coupondropdown.com/uninstall.php
I would do the malware bytes first, and consider the coupondropdown.com site to be suspect, since it has already put this software on your computer without permission.
Best of luck!