When you have to kill a man, it costs nothing to be polite - Winston Churchill
The GA-81915P Duo Pro-A PCI Express uses the Intel 915P chipset for the LGA 775 processor, but includes the Gigabyte enhanced AGP riser (GEAR) slot for people who don't want to plump for expensive PCIe cards yet. The specs for this board are here.
But on page 17 of the manual for this board, in PDF format here, Gigabyte warns that using the GEAR slot might shorten the life of your AGP card.
It says: "G.E.A.R. interface is designed to provide a temporary AGP solution before the mass availability of PCI Express graphics card. It is suggested to use PCI Express X 16 interface graphics card to avoid the damage of your AGP graphics card".
And it continues: "G.E.A.R. interface is created through PCI interface signal and voltage switching to AGP interface, due to this technical specification difference, it might cause AGP graphics card life-span shortens". µ