Have you tried changing the internet options through the control panel? If not, try that.
If you think it's infected, restart and boot into safe mode with networking (F8 on startup). Download, install, and update malwarebytes. Then do a full system scan.
If you can't download malwarebytes in safe mode with networking, download the installer on another PC. You can use a flash drive, CD, floppy...etc, to transfer the installer to the other PC. Then run the malwarebytes scan.