is it possible that a bad ethernet card/port can cause it so I can't set up a wireless network OR is it possible a desktop is too old ( 2years) to run the network? I'm getting a message that my internet isn't connected to the router, but when I have it all hooked up, I can't get on the internet on my desktop

Your desktop shouldn't be running the network. Run the ethernet cable from your ISP's modem/router into your wireless router. Run an ethernet cord from their to your desktop. All should work. It's pretty straightforward.

that's how I had it hooked up, and was getting the message to plug my desktop into the router, when I did that I couldn't get online with the desktop and the router software said internet cable wasn't hooked up

Is it plugged in to the correct port? The cable from the modem goes in to a port separated from the other 4 "out" ports. Cable from desktop goes into any of the other 4.

I know this sounds like a dumb thing to suggest but I did have a friend who had a similar problem to what you described so I went to help him. It took about 2 seconds to realize the cables weren't properly connected.

Cable from modem to WAN port, desktop plugs into any LAN port.