Gabriel Knight 3 will run on xp, just set to compat mod 98. It runs just fine on my older xp,(yr 2001) but with the dual core you have to disable one. (something I haven't learned as yet)
Well, we have an article at the top of the Glitches & Patches forum that tells you exactly what you need to know in this regard: how to disable the second processor for only the applications you want to disable it for
The article is called 'Legacy Games & Hyperthreading', and here is the direct link to it:http://www.gameboomers.com/Members/legacygameshyperthreading.htm
That article was written before the advent of dual core, but everything that applies to hyperthreading also applies to dual core
Just concentrate on the part of the article that applies to using the 'imagecfg' utility, and you're away!