bottom left of the POST screen (disable the abit splash screen) will show it.
You'll see something about award 6 & below that a string of nos. & letters e.g. in the case of my AN8 NF-CK804-6A61FA1-18 with the last 2 being the BIOS version.
Alternatively if you run FlashMenu when it opens it will also show that string.
Thanks Buff. I'm still OCing with just the BIOS and memtest and haven't installed Vista yet. Can't believe this Intel CPU. Got it from stock 2.6 up to 3.5 so far and core temp hasn't budged more than 4 deg C.