I have a simple home system w/ two pc's (Win XP ) on a cross connected ethernet cable going to the ethernet ports built into the mb's. I just purchased a cable modem to go broadband and the store help said it's faster to hook up the cable modem via ethernet vs USB. I have a spare pci ethernet card. Will I run into any problems running two ethernet cards on one pc? Any pitfalls to watch for? Any conflicts?

you may be better getting a router

I plan to get a wireless router sometime in the future, but for now, funds are limited You said I'd be "..better off with a router" and I will someday, but for now can I go the way of two ethernet cards in "master" pc? Is it possible or a huge pain?

It is definitely possible to fit 2 network cards into one system. That effectively turns your master PC into a "dumb" firewall/router. You have one card serving the LAN side (your home Local Area Network connecting to the other PC) and one card serving the WAN (Wide Area Network) side, i.e. your cable modem connecting to the outside world.

Whilst I know it's possible, I've never tried it myself. It should be reasonably straightforward if you've got a very good document to walk you through it. Unfortunately, good documentation on this subject is in relatively short supply (the first 40 results I looked at in Google didn't help) as most people would save themselves a lot of time/hassle and buy a router or leave the modem on the USB port!