The PC provides at most 1/2 the power of the charger. You sound like you don't have a charger, but you can use any micro USB charger providing 1A, like from a phone. If you have one, plug the Nook and let it charge until it's full, should take less than 2 hours. Monitor your battery use afterwards to make sure it is in good shape.
If you use the PC to charge, it will take at least 3 hours, probably longer.
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