Tiger to Leopard

my co-worker trying install leopard on macbook intel core duo, has tiger on @ moment, when tries install leopard on it gives him error saying can't install leopard because has higher operating system installed, had online can't seem find people problem, ideas?
time
ric

 

what exact mac os x version installed?

identify mac , mac os x version, visualised in more elaborate image
identify mac , mac os x version using 25 second video tutorial (3mb, .mp4, h.264)​

and on kind of media come leopard on? grey restore dvd of mac, coloured retail version of 10.5 or cpu-drop-in upgrade dvd?

 

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