Dell laptop vostro 1000
Battery is not work more than 30 mins. after full charging

I purchace my dell laptop vostro 1000 last year in november. But before completing one year it shows battery problem like battery back up is only 30-35 mins after full charge. & it shows one line at the time of starting of laptop " The battery cannot be identified, this system will be unale to charge this battery so pls. solve my this problem as early as possible its so important for me.