Hello joeteds,
you
may find the drivers your looking for at the site below, it's a 3rd party site so i dont know if they will suffice.
Download Drivers - Bios - ASUS - P4P800 SE - driver8146.zip
Do you know the make and model number of the network card ?.
The only problem i can see is that Asus dont offer any drivers for your motherboard under Vista, i think you should get in touch with Asus and clarify this before you waste a load of time on this.
The link below will take you to the Asus forum for your motherboard, i would check there in the post's to see if there are any fix's for your issue.
Good luck.
ASUSTeK Computer Inc.-Forum-