The only way to ID your mother board is to take your case apart. Then write down as many identifying #'s and characteristics as possible, such as number on the chips like your BIOS ID, any other important chip IDs, the number of peripheral slots like 3 PCI, 1 AGP, 1 ISA, and 3 EDO memory slots and any other info you can find printed on the board.
Then either use search engines to find the manual or go here, these guys are good they've ID'ed every MB i brought to em in less then 15 minutes.
http://www.motherboards.org/forums/viewforum.php?f=2