How can I install codecs to MP4 player with hidden operating system?

I have a no-name MP4 player that has its operating system (Windows?) on a hidden SSD partition that I can’t access.
It’s a Rock chip unit and won’t play Xvid or divX files.
Can anybody advise on how I can access the operating system and install the Xvid codec please?

i have been instal mp4 player 10 in 1 from well,but i can’t see anymore my music or videos saved on the player on my computer.please help me