Your hdd may be dead, or not fully dead but damaged to the point where system can see it but its unaccessible, which possibly causes the "hanging". Had a situation like that few times building PCs and hdd was always the culprit. I dont know why it affects POST though. If you know how and feel confident enough than open your laptop, unplug the hdd and try booting(if you dont than get somebody to do it for you). If it posts than you know what the problem is.