I've been dogging this issue with Intel since I first purchased the DP67BG motherboard. This is one of several issues with the board for which I RMA'd my first DP67BG board.
Essentially during POST, you are supposed to be able to press the F7 key and be taken to a BIOS flash update screen. In reality, this seldom works. In most instances the system ignores that the F7 key has been pressed and continues on to boot Windows. In other instances, the Windows Boot Manager screen is displayed. Seldom does the BIOS flash update screen appear.
It's not a matter of pressing the F7 key at the appropriate time -- as some on these boards have suggested. Logically this never made any sense because no such issues occurred with the F2 (to enter the BIOS) or F10 (to get the one time boot menu screen) keys.
Well Intel has confirmed that it is an issue with the board. Apparently, the F2 and F10 are in a special queue where the keypress is stored and the bios will restart posting to make the F2 and F10 keys work. F7 however, was never included in this queue in the original design. My Intel contact is not sure whether there will will be or could be a fix for existing boards. My contact's suggestion is to press F7 just after the numlock light comes on on the keyboard. I've tried this, but for me, it doesn't make a difference. It's still almost always ignores the fact that the F7 key has been pressed. Your mileage may vary.
There are other ways to update the BIOS, so in the overall scheme of things this may be a big "who cares" to many. However, it's just one of many issues and flaws that this board has including: