my computer crashed and i made it but al the stuff were gone. So i installed bf2 again and i patched it....but if i start it up it comes to the login screen. than goes my screen black, than i see the login screen but i cant do anything and than i went again to black. but my computer is not off. When i do Alt+tab i see the formats of my computer screen are different first was is 1024 × 768 and when i start bf2 it wents to 640 × 480. and i have updated my videocard
Your computer crashed and you booted it back up and your HDD was erased? Sounds like a virus to me. I would format and reinstall Windows.