Mac Pro: Kernel panic during HDD boot and DVD boot
It is probably your video card.  The 2007 MBP's were prone to this.

Here is how you can tell.  Download the Ultimate Boot CD.  Burn it to a DVD or a USB Stick

You will launch Linux with a ton of useful diagnostic tools.  Run everything, but especially the video display diagnostic tool.

Mine was throwing errors and I was able to definitively find the cause of the problem.  I was able to find a guy in Tampa that would upgrade the video card on the Logic Board for about $100.  I did the service and it worked great. MBP still running to this day. Let me know if you are interested and I will post his info.