Do a search on Microsoft's knowledge base, and find that QoS packet scheduler pretty much does nothing unless an application specifically asks it to, meaning it does not reserve any bandwidth at all unless a QoS aware application requests it. Therefore the assertion that it gives higher priority to any particular type of data is incorrect. Internet Explorer will not request any bandwidth reservation for any particular data type, to my knowledge.
It also isn't exactly "higher priority" that is being done, it is just a reservation of bandwidth for a particular application so that the application is guaranteed to be able to transfer at a minimum speed. This isn't the same as prioritizing any traffic, it's just bandwidth allocation based on application. The application could be transferring any type of data it wants, it just asks for a set amount of bandwidth.
Additionally, it is reserving bandwidth based on your LAN connection. So if you have a 10Mbps wireless card, and a 1Mbps Net connection, the QoS scheduler (if an application requested reserve bandwidth) reserves by default 20%, or 2Mbps on your wireless card. This isn't going to have any direct effect on the bandwidth made available to your particular application unless you're transferring the data from a server on your own network which is able to feed at that speed, because the 1Mbps connection is going to be flooded out by all your data transfers, not just the one for the QoS application. The QoS scheduler just reserves local bandwidth as well, it won't control the number of requests or anything going out to the router/firewall, so another application could still easily take all the available bandwidth, but as far as WinXP is concerned, it is still making sure that you have 20% available for that application on the local side. (QoS packet scheduler is essentially useless for anyone who does not use a Net connection directly on the machine rather than passing through a router or firewall, or who isn't using QoS for local traffic. However if you're not using a QoS application, the scheduler won't even be active. I personally just remove it from the networking configuration and have done with it. It certainly can't be active if it's not installed, despite the tweak sites recommendation to install it and then manually set it to 0%.)
