Vista - resource conflict (code 12) => no aero

HI,

I own a computer with the folowing components and i've big problems with
windows Vista RC1 and beta2:
ASrock 775XFire-eSATA2 with Intel 945PL chipset
Gigabyte GV-NX66L128DP PCI Express vga with GeForce 6600LE Chip/128MB
Intel Pentium D 930
1024MB RAM

The computer reports a resource conflict between PCI Express root port and
the vga card. So I can only use the vga in safe mode. I've tried both the
integrated vga driver and the new 96.33 nvidia reference driver for windows
vista. I also tried installing the intel chipset inf file. I installed the
32 and the 64 bit version of windows vista. With older windows/windows64 and
linux, the computers working fine. I've tried many different bios settings
(using the newest mainboard bios 1.20) without success. What else could I
try?