Mp4 player mp-185 'sony' info?

[POTSheep]

was recently given this by a mate and cant seem to get any info on it (Pics attached). The only markings on it are Mp4 player and mp-185 (the back cover is missing so maybe theres more on that) it takes a standard nokia battery, on start-up it flashes a sand-timer then the sony logo and then the main menu. the firmware is core: ACT9x0_.43 date; 2006-4-25 fw(?): srx-1.5c-001 date 2006-10-10 has a firmware upgrade option but dosent seem to do nething.
Has a music mode, movie, record, voice(record playback),radio, pics, text and game. Have no idea what formats it plays as it was blank when i got it. i cant find any system folders when i open it just one called record
basically i just wanna know a bit more abou it like would it be possible to but a new os like rockbox or similar on it r new games or nething. Any help is much apprecitaed
sound, Marcus

PS , is actually in colour but couldnt find my camera so scanned it and screen went gray for some reason