Help with router setup

OK, I have a satellite modem that was previously setup with my desktop. Now, I have purchased a linksys wireless router (WRT54Gv5) - (actually I have also tried a D-link rounter also, with similar results). When I try to setup the router with the original desktop, The destop computer will not recognize the router. The router seems to be working properly because I have connected two other laptops to the router with a CAT 5 cable and can reach the internet. I have also disconnected the LAN cable from the laptops and enabled the wireless, and they can connect that way also.

So, as I said, I believe the router is working properly, the PC just won't talk to it. Now, if I unplug the desktop from the router, disconnect the router from the modem, and plug the desktop back into the modem directly, the desktop will connect just fine to the internet.

I've been through the tech support from Linksys, as well as with D-Link. They both came to the same conclusion: the router is bad and I should swap it out for a new one. I did this once with the Linksys router, and had exactly the same results with the second one. Linksys again recommended I return the router for a new one. That is when I bought the D-Link and tried it, getting the same results and same suggestion from their tech support. I cannot believe all 3 routers were bad, especially since the two laptops connected fine.

Anyone seen this problem before?

Thanks