Upgrade from Leopard to snow Leopard in Mac Pro

Hi all,

I am using a (iMac) Mac OS X stall DVD to upgrade my Mac Pro (intel xeon cpu / 4Gb ram) to snow Leopard, but a msg " mac os x can't be installed on this computer" is displayed what every I boot from the install DVD or insert the disk and run directly in desktop. does anyone know what's the issue?

Is it the retail OSX disc?

The install discs for your iMac (grey coloured discs) are specifically for that machine.
You will need to purchase the retail version of Snow Leopard available for US$29 from Apple, also on Amazon, Apple resellers, etc.
Mac OS X 10.6 Snow Leopard - Apple Store (U.S.)

Yes I think so , It's the disk included in my iMac package.

Anyway, thx all for your help !