Usually the battery should not drained beyond the point where the clock stops working. However, if you did drain the battery too much, the clock will reset as they is simply not enough power to maintain it. By the way, over-draining is a major cause of battery damage and I will advice you not to drain your battery in this fashion (or you will kiss your battery goodbye very soon).

Once the clock is reset, there is nothing you can do except format the player so the old license will be deleted. My advice to you is, charge your battery more regularly.

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