Increase Your Internet Speed 20% Reserved by Windows

Microsoft reserves 20% of your available bandwidth for their own purposes 

like Windows Updates and interrogating your PC etc

You can get it back:

Click Start then Run ( Win key + R ) and type "gpedit.msc" without quotes. This
opens the group policy editor.

Then go to:

--> Local Computer Policy
--> Computer Configuration
--> Administrative Templates

--> Network

--> QOS Packet Scheduler

--> Limit Reservable Bandwidth.

Double click on Limit Reservable bandwidth.

It will say it is not  configured, but the truth is under the 'Explain' tab i.e." By default, the
Packet Scheduler limits the system to 20 percent of the bandwidth of a
connection, but you can use this setting to override the default."

So the trick is to ENABLE reservable bandwidth, then set it to
ZERO and press OK. This will allow the system to reserve nothing, rather than the
default 20%.It works on Win 2000 as well.