Try searching your computer and browser for something along the lines of "Search conduit" or "Search project".
Search conduit is a piece of malware that can sneak onto your computer to prevent software, extensions or websites to change your internet default settings like homepage or default search engine.
Yeah, use MBAM in combination to MSE. If one doesn't get it, the other will.
In the mean time, try to think of all the shit you've downloaded and think if they could have caused any problems.
No internet from anything but Steam, and now bingification?
Sounds like Micro$oft witchcraft.
I never considered the possibility of a virus, I guess I should've been more paranoid when you asked me several hours ago :x