Originally Posted by
snootyjim
Okay, so if the exact same cable plugged into the exact same port on the router gives 100Mbps on the PC, and 1Gbps on the laptop, without changing any settings whatsoever, that would pretty much eliminate everything but the PC.
I can't think of any baisc reason why it wouldn't work properly, which leaves a hardware failure of some odd description (seems weird though, not to fail completely) or a software/driver fault.
The best way of testing the latter, to my mind, would be to use either UBCD4Win or a Linux LiveCD and boot into one of those instead of your normal OS. If you can get a gigabit connection on there, then it strongly suggests that some part of your Windows install is borked, possibly drivers.
If that still doesn't work, then it suggests that there's a problem with the actual slot or chip, and the easiest solution would probably be to buy a cheap network card like this:
EDIT: Just a long shot, but are there any compatibility options or similar relating to the Ethernet port on the BIOS?