it won't install the driver..

okay.. let me put this clearly again.

On my first pc, the Ethernet port is connected to the motherboard (onboard ethernet port) the light is still on when I plug out the cable. (i'm not sure if the light should always be on or not) so, i'm assuming the port is spoilt since the light should be off once you remove the cable? windows error msg shows please install driver if you have a network adapter (windows 7) - but cannot install cause cannot detect under device manager - if the port is onboard port can it be detected under device manager under network adapters?

On my second pc, the Ethernet port is a separate card connected to the motherboard (RM50) and doesn't light up even after I plug in the cable. (Card can be detected under device manager and it says device is working properly)

On my modem currently, there is no light on all 4 Ethernet ports. Other than that, all wireless devices are working
I'm probably suspecting the port on my first pc is spoilt and the modem is probably faulty also on the Ethernet cable side.
update : i noticed my first pc's lan port has 2 lights (1 is off, the other is on, yellow colour)
motherboard model is P67A-UD3-B3