The infamous warez and hacking group 'Razor1911' has successfully hacked Shadowrun to be played under XP, without any need for DirectX 10.
Apparently the crack just demands that you overwrite a few files in the installation folder with the ones provided by Razor and the game will run happily under XP.
The information text file that ships with the crack states: "Tired of waiting for Falling Leaf to produce drivers so that you can playShadowrun in XP? The wait is over, because Razor1911 already has the remedy! Yes, you read right. This game will also function in Windows XP".
Falling Leaf Studios had previously reported that they were working on the 'Alky Project' that would contribute 'Alky Compatibility Libraries' to allow the successful running of Halo 2 and Shadowrun on Windows XP machines.
Looks like it was a lot simpler than that.