The file format is entirely proprietary so you are not likely going to be able to find its format or a program that can read it.

From within windows you can still use the dos debug command to unassemble the bios in the F000:0000 block, but these days, the system bios is much larger than 64 or 128k, so only some of it is visible in that area of memory ( the 16 bit compatibility part ). Where the rest of it is kept is entirely up to the bios, and making it visible typically involves setting a bit in a hardware register somewhere that changes a block of ram addresses into the full bios ROM. The details of that are chipset specific, but it is going to be accessible only in protected mode. Manipulating the hardware registers and accessing that memory are not possible in user mode.