(Q) help my xperia m only red led only... topic

hello everybody...
i've got a problem...
my sister just play a some game and after that phone is suddenly death and only red led indicator...

-i'm using flash with flashtool but say unidentified device when installing driver..
and finally say device unplugged after not succesfull installing the driver...
-i'll try to connected with sony pc companion and say not connected but device detected only 2 seconds and not detected again..

can anybody tell him what a problem??
or only battery it's really down??
i'm charging around day and only red led indicator it's appear...
thank's for your help...