On a cold boot of the computer, unplug the HP printer, power up the printer and then after the computer is fully up, plug it into a USB port. Windows should detect it and after a few minute say it is ready for use. If you are on a older OS like XP, you may need to reinstall the printer drivers. This happened on my XP box about 3 weeks ago. One day printer was fine, next day it was gone. Had to redo the driver install (took about 1 hr until it was working)