Install System.kext v9.5.0 as it must be the same version as kernel.
Be noted that System.kext 9.5.0 is included in Voodoo kernel package.

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Only problem I have with Leopard v10.5.6 on my AMD machine is System Profiler. It won't show comp info. Anyone has 10.5.5 version of AppleSMBIOS.kext? It's needed to fix this? Please someone drop me a PM if you have a minute to send it to me (working AppleSMBIOS.kext). Once I get it I'll edit this message to remove request. Thanks in advance.