Had to replace modem and now DSL is very slow

I'm running 2004.1 and when I got a new modem, my access to the internet got really slow. when I use the boot disk, the internet is still really slow. However, when I use a boot disk from 2003 the internet works great. I've been waiting until the new version comes out to install it, however, I can't wait. I need to do something. I don't want to install an even older version than I'm already using.

Thanks