Yesss, I finally made it! Actually I signed up here only to share my experiences:

My configuration is a notebook with ATI Mobility Radeon X700 Graphics and Vista Home Premium installed.

The first problem was getting after the annoying SecuROM message, that told me, I was using some kind of disc emulation software (which I was not!). SecuROM support told me to download a new exe file from http://www.securom.com/support/cus [...] wkotor.zip

That worked fine, but only to let me run into another problem: A message told me that KotOR would not work anymore and I would be notified, if a solution was found. After doing some research I found the reason in the "little bit different" OpenGL support in Vista.

So where to get the required ICD driver for my card? ATI does not(!) provide drivers for their mobility chips, and my notebook vendor is... well... :zzz

I was about to do a complete reinstall of a combined XP/Vista system, when I found this very helful tool: http://www.driverheaven.net/modtool/

This converts desktop drivers from ATI into their corresponding mobility versions - and voila: All OpenGL issues with several games went away at once.

I'm so happy that now I can play my all time favorite game under Vista, and I hope that this info helps other KotOR fans out there.