I recently reinstalled windows xp (sp1), and set up my internet. Now my internet (adsl) goes extremely slow, compared to before the install. also, my other computer (on the hub) goes slow as well, but only when the first computer is online. when i disconnect from the internet on the first computer, the second one goes at normal speed. does anyone have any idea what could be causing the problem?

sounds like you caught a virus while installing winxp again and while the computer is online it is trying to selfpropergate over your network, causing heavy network traffic.
I suggest scanning the computer for viruses. btw, are you behind a firewall?

use netstat to see what connections are open.

Here is a online virusscan if you find any remove them Trend Micro's Housecall.