Or you could try to see if it's a browser plugin that's you can disable and delete. Worked for me when that same thing was going on. A reformat is really extreme. I've manually deleted multiple viruses before, and yours sounds like just a malware plugin.
One virus that hit my parent's computer was really bad. It disallowed any access to any system controls, except the program manager -- though you could not end the process -- resisted any attempt to delete it, and wouldn't even let you get onto the internet without telling you that your computer was "in danger".
I started that sucker in up in safe mode, which disabled the use of the virus's registry entries, then I looked up the exe name in MSconfig, used the search function to find the exe, and renamed it to keep if from opening. Searched through the registry for the filename and edited out all instances where the filename was included, and restarted the computer. The computer worked a little slower and weirder, probably because of registry entries that were edited by the virus to add loopholes and crap, but my parents were able to get all their data easily, and probably could have used it if they had been willing to put up with a little extra slowness.
All this to say that you probably don't have to reformat.
