It's dead almost certainly by what you've tried. Last gasp attempts: Hold power slide to left, connect to rear port of PC and hold to left for as long as possible [at least several minutes]. If it doesn't wake up, open it again and disconnect the battery for an hour or so preferably overnight. If neither works strip it for parts because someone's played with it a bit too much and killed it probably. I've got a 265W and 255W from ebay like that, dead as dodos nothing worked to wake them. Happens eventually to us all who buy 'bricked' units cheap. The mongrel who sold me the 255W had even substituted a non-working screen and dead battery so only the case was immediately salvageable after i went to the trouble to swap both screen and battery to another working unit to test.