Desktop woudnt reconize new modem, but laptop do!

[Ladolora]

I've have Verizon internet, trying to stwich to Cox internet, the moden I have is a Motorola sb6141, when I plug it to the desktop I will not get any internet signal, the link light in the modem wont even come on at all. When I plug it to my laptop, light inmediately come on and the internet is working right away; At the begening I thought the port on the modem didnt work, but after plug it to the laptop I could see that was not the case. The ehernet port in the desktop in working too, i know this because when i plug Verizon modems cable in the same exact port... The internet works again!!!!
That tells me that is not a hardware issue, but again im not sure whats going on.... I have Vista on my computer.

I appreciate the help guys

 

[wacabletech]

After you plug it into the desktop, power cycle it [pull power from wall and then plug it back in], they log MAC addresses and do not talk to new devices, this is why you get a router and use both devises off of it.

 

[Ladolora]

Already tried that....didnt work, thanks anyway
Any other sugestion?