Any Idea what the problem is?

I need to know if this is based of my bios config, or if my PC is just underpowered. (I'm working on getting better CPU more ram and Better GPU)

I'm saying this because right now my hackintosh is running 10.6.3. Any Higher and it fails to boot with verbose saying [PCI Config Start] or smth.

-Specs ATI AMD Radeon 1300/1500 Celeron D 3.20 G/H 1gig of DDR2 ram. I forgor motherboard (BIOS is American Megatrends. NO company branding btw. just HP splash screen. and recovery option.. It's a HP Pavilion a1410y.)

-Edit I did upgrade GPU from the original xpress one. still ATI