Unable to boot from CD or USB

[Life,Death,Tech]

I'm trying to do a clean install of Snow Leopard on my friend's MacBook Pro. He's currently running Lion. I have tried to boot from both a 10.6 CD and a USB image, but it just hangs on the grey apple logo with no spinning wheel. I also tried to run Disk Warrior from a CD, but it wouldn't boot that either. The CDs and USB work perfectly on my MacBook Pro, so that's not the problem. I tried resetting the NVRAM and PRAM but that didn't help either.

Any idea what could prevent a MacBook Pro from being able to boot from any CD or USB image? Thanks for the help.

 

[macbwizard]

How long did you wait on the logo screen?

 

[bozz2006]

Are you trying to install Snow Leopard on a Mac that shipped with Lion? It tries hard to not let you do that. I know theres a way. Check it out.

 

[Life,Death,Tech]

It's a 2009 unibody MacBook Pro and has previously run Snow Leopard. I waited over an hour on the logo screen.

 

[bozz2006]

Have you tried removing his hdd and hooking it up externally to yours to erase the disk? I'd try that and see if you're able to install snow leopard once the disk is wiped.

Also, is this a retail snow leopard disk or restore disks that shipped with a computer? Because those disks are model specific.