run "ethtool eth0" and have a look at the output. It's possible that it's autonegotiated a stupid setting like half-duplex or some lower speed.
Do the same with the windows box; that information is the properties dialog for the network device.
Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!
We don't know who it was that discovered water, but we're pretty sure that it wasn't a fish. -- Marshall McLuhan