dependng on age of motherboard, you might have individual pins type header or a header plug housing , which for firewire is usually green/light green where as USB is most times Blue, if I remember correctly..
as Krusty stated never plug USB into firewire or firewire into USB pin connections on a MB, .......
my new ASUS board has the latter newer type of header plug housing for all connections, USB, Firewire, front audio/mic / case & HDD connections..... where as my older ASUS has the individual pin type connectors for everything.....