Not worth it, in my opinion. But that would be a cool hack. If it isn't already on the board, then you probably can't add it yourself. On the other hand, some resistors and an LED wired up in parallel to the recharge lines on the battery and routed to some optical plastics around the power port could do what you want... Maybe.

FWIW, the glow ring was on the original 300 MHz clamshell iBooks. Mine's glowing green right now.

Peace,
Drew
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Power to the PowerPC!