Radio on '99 Grand Prix Totally Dead

My in-laws just bought a '99 Grand Prix SE used. The red TheftLock light on the radio is flashing and the radio doesn't turn on. It seems completely dead. The battery was dead shortly after
they got the car.
Does the radio need to be reset? How can this be done?
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if they recorded the radio code somewhere--it won't be factory-printed in the manual, but hopefully some thoughtful person recorded it somewhere. If all else fails & Pontiac cannot help either, take it to a competent radio shop and they can either unlock it or send it off to someone who can. Cost me $50, including shipping, on a recent one that was in a used car we had for sale. s
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