QoS Packet Scheduler is a method of network bandwidth management that can monitor the importance of data packets and depending upon the priority of the packet, give it higher or lower priority or bandwidth levels.
Normally, if your system's LAN cards don't support QoS Packet Scheduling, you don't have to worry about it.
But, if you want to disable it, you can change it by doing the following. Note, this is not available in Windows XP Home Edition.
Start Menu --> Run --> gpedit.msc
Expand Administrative Templates under Computer Configuration
Click QoS Packet Scheduler
You will find an entry in QoS Packet Scheduler called "Limit Reservable Bandwidth". Double-click it, enable it, and set it to 0%.
More information on QoS can be found at these links:
Windows Platform Development -- Quality of Service (QoS)
Microsoft Knowledge Base -- Windows XP Quality of Service (QoS) Enhancements and Behavior
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