Did you reboot after making each change in speed and duplex? Did you also try to disable IPv6 in the properties of the network adapter, just to see if that would make any difference. It would seem that you might need to look into a firmware update for your router, or even a replacement if there is no current/reasonably recent firmware updates available. Assuming all your cables, cable ends, wall jacks, etc... are in good repair and undamaged and of course assuming that your cable is not routed across or laying on any source of EM interference, like fans, power transformers, flouresent lights, etc. Then you should be able to get 100 half easily and ideally 100 full.