okay.. well try this

platform=X86PC -v -f
platform=ACPI -v

or else check in bios if you have checked whether you have put AHCI not Native IDE in Sata Type.
sometimes it happens due to incompatibility of the hardware.. Well if this doesn't work, you can use some other DVD like "iPC OSx86 10.5.6 PPF5 Final" or "Leo4all 10.5.2" these are also great working Distro's..