Where would be the best place to start looking to buy a power mac g4...Ebay? and what sort of spec would I need to be able to run mac os x leopard, or should I be looking at a second user G5. Also do I need Mac specific LCD monitor, keyboard and mouse.

I guess eBay is as good a place as any for a G4... if you're lucky though, you might still be able to pick up a G5 tower from the Apple online store's refurb shop. Maybe.

As for Leopard's requirements, here's the processor bit (from HERE (http://www.apple.com/uk/macosx/techspecs/))...

A Mac computer with an Intel, PowerPC G5 or PowerPC G4 (867MHz or better) processor


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:)Think there is one in the for sale section, Seam to remember reading it.

Why you looking for a Powermac? Surely a newer model would be more appropriate? Try the refrub store on the Apple site for discounted models.