I have a Pavilion 23, purchased July 2013. It went to sleep and won't wake up! It has worked fine until now. It went on sleep mode after not using it for a few minutes, and now it only has a black screen. I have tried the hard reset (disconnecting from power and holding the "on" button for one minute, but nothing is happening? Any suggestions? Someone mentioned the power cord to me. Is that a common issue with this model?