I have a Mac Pro 8 Core and Snow Leopard won't install from the DVD.

What DVD are you attempting to use?

If it is older then the version of OS X that came on the Mac, it will not install.

If it is a DVD for another Mac, it will not install.



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Allan

Either your machine doesn't meet the [Snow Leopard system requirements|http://www.apple.com/macosx/specs.html] - which I can't imagine would be the case for that machine, though I don't know that for sure - or you're using the wrong disk. Note that the gray disks that shipped with one machine will not work on a different one, unless they are exactly identical models. Or, I suppose, you've got a bad disk or hardware problem.

Did you upgrade the graphic card after purchase?

ATI 5770/4870 require "10.6.4 or later" so the $29 SL 10.6.0 would definitely not work in that situation.

Snow Leopard doesn't come on DVD with 10.6.4 unless you have a Mid-2010 Mac Pro. Not seeing what exact system it is leaves it in the dark.

Since the OP's running Leopard, it's not a new machine. 😉