Windows Vista/7 has a network setting named "task offload" which is on by default. What this does is take same some processing away from your CPU and hand it off to the processor on your network card i.e. computing checksums and such like. This should give you performance benefits.
Turning task offload off may speed up the copying of large files over your LAN with Windows 7. You need to open a command shell with admin rights. To list which interfaces have task offload switched on:
C:> netsh int ip show offload
To switch task offloading off (globally):
C:> netsh int ip set global taskoffload=disabled
This should return "Ok". Now disable and then enable your network adapter and it should be done. Try a file copy.
