problem booting precise from external hard drive
I have a Seagate external hard drive that has a copy of 12.04 on it. I also have a HP laptop with Windows 7 Professional as the base OS. I am trying to set the system up so that when I start up the laptop I get a choice of 12.04 or Windows 7. As far as I know, this can be achieved if the boot order is set so that the system can boot first from the external hard drive. Here's the problem: When I hit F10 during POST the window that shows up does not give me any options to change the boot order, as far as I can tell. In fact, none of the options that are presented by hitting ESC during POST seem to give me the ability to change the boot order.
Could someone more experienced in this problem give me some help. I've been all over the web looking for a solution. All the solutions I have seen presume that the user can get to a BIOS screen that allows the user to change the order. My Windows 7 doesn't seem to present such a screen. I don't get it.