Why don't you reflash the phone, if it refuses because of battery need charging first, then try this, press power and hold button and connect charger cable, if the charging light on then release power button and let it bee few hours, disconnect and turn it on, if starts to boot then shots of itself, then other way round is if you had installed nitdroid then boot nitdroid and check settings/battery, if needed charge it, but not with computer USB port!
After my experience, when changing computers...the phone fails or refuses to activate charging thru USB as one excuse there is not enough power from computer USB to charge the phone, and in this case i guess when you connected your phone with computer to transfer your music files, probably you were happy you connected with computer and you thought everything is alright, and you didn't bother if it's charging or not, the battery must have discharged completely instead, it just happen to me last night similar problem for the second time, but i solved problem after few times attempt powering up the phone!