Here is what I would do. I would strip the system down as bare as it can be. Nothing connected to usb, firewire. Anything that can come out memory, wireless nics, blue tooth adapters. Pull it out. If you do not have memory built into your motherboard that will need to stay in.
Try a different cd drive?
If it is failing at the same point of install – what does it say on the screen when it fails? Does it just freeze or is there an error message with it?
Have you checked the error log?