I found this in a few different places around the 'net - hopefully it's helpful:
This is for broad band connections, though it might work for dial up.
- Make sure your logged on as actually "Administrator".
- Start->Run->type gpedit.msc
- 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.