I was working at a computer that couldn’t get far on the Internet without this annoying page popping up.
The site producing this page is pc-support-messages.com, which is one of the nastiest browser hijackers I’ve seen. You can only go to a few web sites before this hijacker kicks in and takes you to the page claiming your computer is infected.
I attempted a reset of Internet Explorer, which didn’t fix the issue. I also ran a scan using the Malwarebytes Antimalware scanner, which found and removed the malware, but the problem still persisted, much to my surprise.
I think what saved the day was the HerdProtect scanner I keep on the flash drive attached to my keychain. It too found some malware, and after removing them the problem finally disappeared.