my sharp gx15 has died and will not turn on this is because battery ran out though unlocking. i have heard that you can reflash it via the hidden/secret/engineres menu - the only problem is i dont know how to get to this.
can any one help as my phone is 5 days old

Why not try and take it back then if it's only 5 days old? Are you on contract because they should definitly replace it then? otherwise it is at least worth a try...

why not just take it back and not say anything about it and get them to change it, for a new one if not get your money back as its under 14 days old
by any chance you did not get it form the dsg group did you. as if you did that is why it is playing up