how to install os 10.6.7 on macbook os 10.5..8

You need to install Mac OS X 10.6.3 from a retail DVD(the online Apple Store sells them) and then run the 10.6.7 or 10.6.8 combo updater.

All Mac OS X 10.6.7 DVDs are specific to the Mac model they shipped with.

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If you previously installed it from a retail DVD and updated it to 10.6.7, yes. If it's a MacBook Air's install thumbdrive, no.

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No; it's either a MacBook Air's original thumbdrive, in which case it can't be used on a different Mac model, or it's a working copy of the OS and doesn't contain an installer.

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