tl;dr- spamsite loads as homepage, need help fixing it

So I'm at my wits end trying to fix this problem. Whenever I open a browser, I've tried both Firefox and IE, it loads this "instantpharm.com" thing as the homepage. No matter how many times I set it back to google, if i close the browser and open it again, it loads the same spam site. So far I've scanned with AVG, Malwarebytes, and CCleaner but none have detected anything.

I've checked the Mozilla support site and found a few others are having the same issue, however there's no solution posted.

Any help or suggestions you guys have would be greatly appreciated.

Also, before anyone says it, this is my school laptop, so there was no porn viewing whatsoever done on it. Whatever this is, it came out of nowhere.
Currently listening to:
Mock Orange
Tiger's Jaw
American Football