The fix is rather straightforward, you need to run several commands in the command line as an administrator. Start with netsh interface tcp show global which displays the TCP Global Parameters. One parameter listed is called Receive Window Auto-Tuning Level which can be restricted, disabled, normal or highlyrestricted and probably several other that are not that important for the solution.

The command netsh interface tcp set global autotuning=disabled disables auto tuning which should lead to a speed increase if your computer experienced slowdowns and connection errors. Setting autotuning=normal returns to the default state for the autotuning parameter. Some suggest to set autotuning=restricted before disabling it fully or to autotuninglevel=highlyrestricted.

I would begin with restricted, if that does not help I would change to highlyrestricted and if that does not have the desired effect I would disable the feature completely.

The test itself could very well take up to ten minutes, mine took about seven I think. Every phase of the test is explained to give you an understanding of what is tested and how this technology is put to use in Windows Vista. Microsoft points out that the test should not normally affect the internet connection which I can confirm. I was downloading a large file while the test commenced and it did not stop or slow down the download.

My router passed all of the tests, what about yours ?

Found at Pimpyourwork