I have a Compaq Presario SR5129UK which I've added a NVIDIA 9500GT 1GB graphics card into in aims of installing either Leopard or Snow Leopard onto, but I have a bit of a problem...

When i go into my BIOS I have no option to change to AHCI mode, which I believe is needed to run Leopard or SL?

I've tried to install iDeneb and iAtkos onto my system but neither will load, I get a "stop sign" on the grey screen after a few minutes, I've also tried to install both via Virtualbox but neither work (iDeneb installs but after i unmount the CD to restart after installation, it goes to a blank grey screen and hangs)

What are my options? here are my computers specs (screenshots taken from CPU-Z):

Compaq Presario SR5129UK
CPU
Caches
Mainboard
Memory
Graphics

massive thanks to anyone who can help me!