wow, this manual kind of sucks, but I think I found the header! If you look on page 3-1 of the manual there is a pic of your board layout. The header is a little to the left of your 4th and 5th pci slots. if you're not looking at the manual, you should still be able to find it, just count pci slots from the top (next to the AGP) down to the bottom (next to the ISA port) Let me know if you find it.