Trying to set up network with (wired) Mac Pro and Windows laptop

I'm trying to set up a network using Airport Extreme (pod-shaped version) and a Mac Pro (using a wired Ethernet connection, no wireless card) for use with guests who bring Windows-based laptops…is this even possible? I've heard some people say it usually just doesn't work for some reason…I've tried switching the password to WEP from WPA2, but I don't remember if I turned on Internet Sharing or not (they're not here right now)—is that necessary?

I'm wondering if it's even worth trying to figure out, and/or if upgrading to a 802.11n AE will work better (or at all)…also would adding a wireless card to the Mac Pro do the trick? (under either the current AE base station or an upgraded one). I didn't realize Mac Pros are difficult to install wireless cards in, so the process costs at least $100 (approximately), I'm trying to avoiding sinking more money into the setup unless absolutely necessary.

P.S. I have Verizon DSL, with the basic Westell modem they sent me a couple years ago when I signed up. I also have good quality Ethernet cabling (RJ-6?) cause I've heard that makes a difference.

I have three computers, an emac, an imac & one pc laptop. My 6 year old emac connects to the internet via ethernet, but the other two (an imac & the pc laptop) can connect to the internet either via wireless or by ethernet.

Each ethernet cable (cat 5 patch cable) fits directly into my router's ethernet ports (there are 4 ports on the router).

I had no difficulty setting up the ethernet connection. I attached each cable and the computers were on the internet in a moment - nothing to download, not even for the pc.

With regard to wireless, my imac managed the connection without any difficulty, but the laptop had an old wireless card, so I needed help configuring the laptop's set-up. I also had to downgrade the encryption from WPA to WEP.

I did not need to turn on Internet Sharing.

The three computers can now go on to the internet either separately or together and in any combination - either by wireless or ethernet.

You do not need a wireless card in your Mac Pro. Nor do you need to make any changes to the settings of your Mac Pro.

Only need the Mac Pro to use Airport Utility to set up the AE. You might try putting a $ in front of the password on the AE and have the Win users not put in the $ when they enter the password on their machines.