|You might need to change the settings of reserved bandwidth|
Check out these steps
type GPEDIT.MSC in search box
then a Group Policy Object Editor will popup.
Under Local Computer Policy
click or expand Adminstrative Templates
next click or expand Network
then click on Qos Packet Scheduler (remember dont click on the expander here just click on Qos Packer Scheduler)
Now double click Limit reservable bandwidth
(You will see Not configured which is the default settings but in reality Vista has already taken 20% of your bandwidth to reserve for updates and stuff like that.)
Now click on Enabled then in the Bandwidth Limit (%) set it to 0 then click apply then reboot.
tried it and it does work. no big dramatic gain but it works