Currently being moderated.
maybe it's not a problem with your hardware but with Win7 x64 and the TCP Chimney offload: With chimney disabled the transfer rates workes very well again like in XP where chminey not existed:
To disable chimney type the following command as admin in the command line (but that's without any warrenty):
netsh int tcp set global chimney=disabled
See also KB951037 at support.microsoft.com