Not a virus, but probably some other piece of malware.
The best security you have for your computer is the bit that sits between your ears. I never download anything I do not choose to, and I certainly never download anything if something from and unknown publisher pops up and tells me my PC is infected or needs this, that or the other piece of software.
Download, install and run in this order :
Lavasoft Adaware, available
here
Spybot Search and Destroy, available
here
Malwarebytes Anti-malware, a link to the download site is
here
Before running each, make sure you get an update for them so that they are looking for everything they can find and remove.