Before you start run a speed test and make a note of the results.

Download DrTcp here - http://www.dslreports.com/drtcp and install it.

Change the TCP receive window to 2000200 and the MTU to 1500 make sure the correct network card is showing in the drop down under "adaptor settings" click "Save" and reboot the PC.

Try another speed test and compare.

If the results are no better or worse (very unlikely) You can run "Tweak Test" it will give you some settings to try -

http://www.dslreports.com/tweaks

You must reboot after every change.