Hip-hipp hooray!!!!
Works like a charm for my GTX 260. Thank you so much - I was already desperate so many things I already tried. But it was woth the patience; I have now a fully working Hack (I call it "MacBobo") on a P5Q DeLuxe with untouched legacy BIOS, Q 9300 @ 2,5Ghz (stockspeed), 8GB DDR 2 GEIL @ 1066 Mhz, ASUS GTX 260.
Initial setup done on a 2nd rig with P5Q Pro mobo and modded BIOS from JUZZI, E 8400, 4GB DDR 2 800 and ASUS EN 8800 GTX EE; then transplanted the HDD into my main rig and everything booted right on exept the gfx card,which is done now also.

Cheers

Info added: Actually I run Slowleopard in 32-bit mode. Once i have all the 65-bit extensions together I will boot into 64bit mode. I hope the gfx card will still work then...