Good News! Windows Vista/7 includes TCP Autotuning. It will use up to a 16 MB maximum receive window. If anyone knows how to increase this above 16 MB please let me know.

Vista/7 also includes "Compound TCP (CTCP)", which is similar to cubic on Linux. To enable this, set the following:

    netsh interface tcp set global congestionprovider=ctcp

If you even need to disable / re-enable autotuning, here are the commands:

    netsh interface tcp set global autotunninglevel=disabled
    netsh interface tcp set global autotunninglevel=normal
    

Note: You'll need to Right-click "run as administrator" for these to work.

There is no way to adjust the default TCP buffer in Vista/7, which is 64 KB. Also, the Windows Vista/7 autotuning algorithm is not used unless the RTT is greater than 1 ms, so single streamTCP will be throttled on a LAN by this small default TCP buffer.

For more information, see these articles:

Windows 7, Vista, 2008 Tweaks

TCP Receive Window Auto-Tuning in Vista

Enterprise Networking with Windows Vista

Why TcpWindowSize does not work in Vista