said by Smith6612:
Do you have auto-tuning Heuristics enabled by any chance on your system? That was introduced starting with Windows Vista Service Pack 1 I believe and it may be adjusting the settings like that. Try disabling it if it's on.
netsh int tcp set heuristics disabled
If it's on can be shown through
netsh int tcp show heuristics
Yes with SG TCP Optimizer it gave me the option to disable it. I verified with your command in DOS prompt and it shows it is disabled.