LAN gigabit working at 100mbps

[edyleca]

Hi
I have a strange problem. I have an Asrock Z97 Extreme4(windows7,64bits) with onboard ethernet adaptor and also a Fiber optic connection of 500mbps. The network adaptor status stays at 100mbps instead of 1Gbps. I have tried to reinstall the driver, I have tried another PCI gigabit adaptor, I also updated the Bios and finally I reinstalled Windows7 64-bits and nothing changed. When I try to manually set the speed in properties of local area connection to 1gbps instead of auto-negociation, it appeares like a network cable is unplugged.
I have to say that I made a speedtest with a laptop and it stays at almost 500mbps, so what can I do to solve this problem?
Thanks