any one can help on setsockopt and tcpwindowSize

any one can help me on setsocketopt.actually i want to increase window's TCP socket buffer size which is around 8 KB by default.
my application need more buffer size while sending data to network so i have to change the its buffer size.i came to know that there is one registry parameter i.e. TcpWindowSize ( check out in MSDN ) which can increase buffer size from setsockopt API but i m not able to get its parameter and i dont have any app example.any one can help ???

thanks in advance ..