This is for broad band connections, though it might work for dial up.
Make sure your logged on as actually "Administrator".
Expand the "Local Computer Policy" branch.
Expand the "Administrative Templates" branch.
Expand the "Network Branch".
Highlight the "QoS Packet Scheduler" in left window.
In right window double-click the "Limit Reservable Bandwidth" setting.
On setting tab check the "Enabled" item.
Where it says "Bandwidth limit %" change it to read 0.
Effect is immediate on some systems, some need to re-boot. This is more of a "counter what XP does" thing. In other words, programs can request up to 20% of the bandwidth be reserved for them, even with QoS disabled.