MP4 digital player. During loading in from Media Player, it suddenly went berserk and appears to

Question

During loading in from Media Player, it suddenly went berserk and appears to have downloaded so much data that on PC it shows the 4Gb memory to be full.
The radio works fine and so does the games section but other categories show,"Disc Empty" except Record which shows "Overflow!"
Can I delete it or even format the 4Gb player and replace the working system.
Don't mind losing any music (if there's anything left!) as it's all on HDD anyway.
Don't want to format without advice and then lose the much used radio as well!