First off, all the names I have listed below may not be the exact same in the english version of XP because I translated from the swedish version.
Start / Settings / Statusbar and Startmenu / Startmenu tab at the top/ Choose the classical setting and click the button next to it /
/Find the scroll area which reads something like "Advanced settings for Start Menu"
/Tick the box which should say something like "Roll program menu"
Now you should be able to scroll through all programs on your start menu by clicking on the arrows at the top/bottom.