To enter the bios: Immediately you turn your PC on start hitting the delete key repeatedly until you get a message "Entering Setup" or similar.
The option to disable virus protection is usually under the Advanced Bios Features or similar. It is toggle on or off the key you press to toggle will be shown at the bottom of the screen.
Once it is disabled, press F12 (usually) but the save and exit will again be shown on the bottom of the screen. Exit saving changes and your PC will boot into Windows.