Today i just found out the some of the Windows metro apps are not working and when i try to start them up and it immediately closes and goes back to the start sceen. And each time i reboot my Windows 8 tablet in the desktop opening up Firefox it keeps asking me to choose Firefox as your default browser and i keep saying yes but it keeps happening. I think i have a virus on my Windows 8 tablet but my Anti Virus(Avast, Avira) did not find any viruses. How do i fix this and the Firefox default browser thing???