The tweak is simple. Beside the QoS and others around the Internet for the new XP OS, I found out that native drivers sometimes slow you down (cable and xDSL users). So if you have applied all tweaks and you are still having slow downs try reinstalling your NICs drivers.
I have reinstalled my NIC drivers (I own a CNET generic NIC, native driver is installed with OS) with the latest found on their website, and now I can really apretiate all my available bandwith. The difference is noticeable. My web pages now load almost instantly where they used to take even a minute!
As allways, this tweak worked well for me, but may not work with everybody, just try! You can go back to native drivers anytime.