I've got basically the same problem (using Windows 7 to move large files to or from XP fails), and disabling autotuning did not solve the issue. I've also tried updating both NIC drivers, rebooting both computers into safe mode with networking, disabling as much offloading as I can for both NICs, directly connecting the computers (with 2 different cables), setting LAN Manager authentication level to Send LM & NTLM, turning Network Discovery off, and turning off IPv6, QoS, Link-Layer Topology Discover Mapper I/O driver, and Link-Layer Topology Discovery Responder. Nothing seems to fix the problem.
I used Wireshark to do a capture
of a failed transfer, but I have no idea what to make of the results. (Note that this capture was done after undoing most of the "fixes" I attempted above.)
Anyone have any ideas what might be causing my problem?