Setting up a home network (general questions).

[venustx3000]

I currently have one HP Desktop (HP Pavilion Media Center TX PC m7640n) and one Dell Laptop (Dell Studio 1535 PP33L) in my study. I have attached the general Cable modem and one wireless Netgear Router (54mbps wireless WG11xv2). We have one HP J6480 Officejet printer and one Photosmart 3180 printer in use. I would very much like to network the laptop and desktop together but there are several questions that arise:
1) If I purchase new software (Windows OS, Norton Firewall, other basic programs), can it be used in the network on both computers?  2) Do both computers need the same OS? Currently the HP has Windows 2000 and the Dell has Windows Visio. 3) Can this system be set up wireless? If so, are there cards for each compouter that I need to purchase? 4) I guess the most important question is do I need a network cable to connect each computer, or can this be completed wireless. Is so, what software do I need?
Any assistance you could offer would be greatly appreciated.
venustx3000

[soybean]

1) If I purchase new software (Windows OS, Norton Firewall, other basic programs), can it be used in the network on both computers?

If the software license agreement states the software is for use on one computer (which is typical), then that's exactly what it means. 

2) Do both computers need the same OS?

No.

3) Can this system be set up wireless? If so, are there cards for each computer that I need to purchase?

Your laptop has built-in wireless, so it needs no card.  The HP Pavilion Media Center TX PC m7640n would need a wireless card if you want wireless capability with it.

4) I guess the most important question is do I need a network cable to connect each computer, or can this be completed wireless. Is so, what software do I need?

I'm not quite clear on your what you're asking here. Do you mean to connect each computer to the router, or what?  If you want to use a wireless Internet connection with your laptop, then you don't need a network cable for it since you have a wireless router.  For Internet connectivity with your HP computer, you need a cable to connect it to the router, which I would think you already have.

If you want to network to two computers, you have everything you need. They can be networked via the router. No extra software is needed; Windows is all you need.