Hey, I can give you everything you need
follow the links.
[HOWTO] Remove DISK ERROR! / Error format etc.. on AK2025
Tutorial on fixing the memory (note: format in FAT not FAT32 as the guide suggests.)
As another note, To find out what the slider number should be, subtract 1921 from the number your player reports. As an example (Memory free:8654MB your slide the bar to 6733 and format.
Format error help.
Someone else with a similar problem, read you might find something that helps.
If you need anything else or are confused about any part of the process, just ask and I'll be more than willing to help.