We need a little background info.... Did you buy a big box pc like a dell or HP? If so on first boot you enter your personal info and then you enjoy your new computer.
Did you build a computer. If so then the HD is blank and you need to install windows. Once windows is installed then you install any missing drivers like maybe the video card drivers and sound drivers.
Normally you dont need to flash the bios on anything unless your having a specific problem that is mentioned on the bios flash release notes for your hardware.