Well, after fooling around a bit with TCP Optimizer on my Vista, I’ve come to find that Vista auto-tunes all TCP settings. It calculates optimum MTU and RWIN automatically. However, there is a way to change the auto-tune levels in the command prompt.
netsh int tcp set global autotuninglevel=
then use one of the following parameters
disabled highlyrestricted restricted normal experimental
These set the amount that the receive window can grow beyond its normal static value. You might try some tests with this. Also it appears that the TCP Optimizer doesn’t function well in Vista and probably Win7.
It seems that when streaming stuff to other devices auto-tune can be a problem often requiring retransmission of lost packets. You might also try the command:
netsh int tcp set global congestionprovider=
using these parameters
none ctcp default
Vista and possibly Win7 defaults to none. ctcp uses a more aggressive approach so this might be something to try out.
And here is a good source of info on the Vista TCP/IP stuff.