Look on your motherboard for a 1394 header. It will probably be labeled, and I'd be very surprised for it to not have one if it's only 2 years old. If it's not labeled, google for the motherboard number and find a schematic.
---------- Post added at 02:32 PM ---------- Previous post was at 02:23 PM ----------
Edit: I just searched newegg for 'internal firewire' and the first hit is an $8 card with one internal header and one external port, the second hit is a $10 card with one internal and two external. Both are in stock. Where did you look exactly that they were hard to find?
Newegg.com - internal firewire