[Android Central Question]

My android phone is dead. It is not starting up & not charging while charger & data cable are OK.

Phone was not in use for 20-25 days & when try to on it, it couldn't start. I try to charge it but it was not showing anything(usual battery symbol). I left it on charging for 5-6 hours & again try to on it but it couldn't start.
It is not showing anything like welcome screen. I tried power button+vol. up/down key but nothing happened.
Now it is completely dead & its warranty period has been over.
I took it to local repairer (not confirm whether had sufficient knowledge of android phones or not) he examined it said "its hardware is OK problem may be of of software." Then he went to another person. He tried to install its software (I think OS). According to him files were written but 2 files were creating problem in writing.