its worked ok for me both ways. your comp auto detectys video adapters so once its installed on the computer it should work fine, just install new one, go to properties by right clicking desktop, go to displays, set card as primary adapter and disable other one. (if you are pushing your PSU to limits you should disable in you driver area. Buit has anyone else ever had a card fail from installing in the wrong order? My MX 4000 is the only card I know that requires only one to be installed.