FireWire and USB

FireWire(IEEE 1394) has gained a very popular reputation. Would there be a compatibility issue if someone where to install a FireWire card that already has a USB connection? If there would be a compatability issue, how would one resolve this? I know they are different cards with differnet standards as well as different software drivers. Trying to be on the safe side. Thank you for the feedback.

Regards
Markus R Bertel