has a full cat-5. I believe it has 2 twisted pairs.

I thought a full cat-5 was four twisted pairs, making the combination of those two sentences a non-sequitr. I could be wrong about that. Edit: Just re-read your sentence. You said DON'T THINK not THINK. Sorry. Didn't realize you were referring to existing wiring. Thought you meant you were doing the wiring yourself.

Anyway, the advantage? If you have four pairs instead of two, you can run 10/100 LAN and two telephone lines telephone together on the same wire.

I've been in enough situations where I run out of in-wall wires too fast and I'm just an advocate of over wiring the in-wall stuff from the start, to plan for future expansion. Someday you might want to run gigabit ethernet across the house. Or maybe steal a few pairs for running an s-video connection across the house. Or something like that. I'm just saying, when doing the basic wiring, it's better to have more wires than you need than it is to run out of wires after the plaster is in place.