Network card not working

I was in the middle of browsing the internte and all of the sudden the NIC in
my computer stopped working for no reason, on the device manager it shows
under other devices with an exclamation point next to it. I tried to unistall
the driver but windows keeps detecting the right card, but it shows always
under other devices. I removed the card and replaced it with a new one, but
got the same results. I don't know at this point if the problem is the
operating system or there is a problem with the motherboard.
Please advice if there is anything else I can do. Two different NIC's with
the same results will let me to believe that is the operating system.
Hope you can help.