Hi Nico,
I see You have hardware similar to mine(same cpu/Video card and EX58 chipset.Have you installed FSX and Acceleration or SP2.Have you experienced any Flashing of your screen with large white or black sections.These are very quick.Also some Vertical Black stripes,seems worse with high graphic settings.
My setup does this if i either load Acceleration or just SP2.Sp1 is ok.
Trying to work out if i have a hardware problem.This was with XP 32 bit.
Ive since upgraded to XP 64 and it is very much better.
Be very interested in your comments.