well, with 2 NX8800GT Zilent, there's no need to move one to the white PCI-e : there's enough space for the X-Fi to go in the free PCI-e 1x slot remaining. anyway, this fixed the problem, but not completely. this is not worth as it was, but there are still some glitches, scratches, etc...

thanks for the link loonym, I'll give it a try tomorrow after my job day have to take some sleep after this 2 days testing session...

also thanks for the tip with driver cleaner pro (will go in my survey utilities folder), but I already made a drivers free XP image, so I just need to redump it