Ok a few things I need to know. 1) The adapter came with your monitor yes\no. If yes then it might not be the right type. I believe there are three types of DVI. It may look like its fits but may not be right for your card. Have you tried both heads on the card (video to monitor hook-up) ? 2) The MOBO you said is a P4P800? if this is true all the P800 Asus boards only support AGP cards 3) Take the card down to a local shop and have them plug it in to a lab PC and see if it works for them.