After repeative w7 64 LAN driver updates the negotiated speed was bumped up to 1 Gbps.
I downloaded and installed LAN driver 5/14/2010 v.15.3 several times as device manager network driver properties refuses to display anything but 12/04/2010 v. 126.96.36.199 MS Windows Hardware Compatibility Publisher. To my surprise finally after hours of troubleshooting the negotiated speed was raised to 1Gbps.
I haven't checked with to updated XP drivers but used just ones supplied on accompanying CD.
It leaves me into confusion - is there a flaw in motherboard hardware, drivers or drivers installation?