Marix , i'll suggest a format using MP3 Utilities Disk Tools, the guide is here
http://www.mympxplayer.org/how-to-re...ck-vt2400.html
It seems that your player has hacked memory, causing the "Format Error" and file duplication. After formatting, your player would be returned to its original memory capacity, and those problems should not happen again.
You can download any version of MP3 Utilities in the downloads section here
http://www.mympxplayer.org/mp3-playe...ties-dc44.html
It would contain the required Disk Tools needed to format your player.
For video, your player reads .AMV video format. You'll need to convert using MP3 Utilities again. What is your screen size?