AFAK the best option is Multiboot.
Do a factory reset, and install firstly logo, later _uboot and finally an official rel.15 in flash, RS-232 via, of course.
thanks a lot Malparosa but I know how to factory reset, but I cant do how to install a logo, i dont know who is _uboot and how to flash, and I dont know where looking for official rel.15, can you help me???