For instance most PCs can handle VBR encoded files (sorry I will not write about VBR or encoding of MP3 files here, use google) and your player may only handle some list of MP3 encoding. Go outside the list and this happens.
A few weeks ago I transferred a number of MP3 files from a computer to an MP3 player (TWF Audio 0.5 Gigabyte). I have since noticed that though when one plugs the MP3 player into the USB socket of the computer, one can see (and play) all the MP3 files (which amount to more than 100) not all these (probably 10-20% less) show on the screen of the MP3 player (and thus cannot be selected and played). Why should this be - is it something to do with the software on the computer windows Media Player 11) and the MP3 player (dont know what this is called) being different? Would it also occur on a larger capacity (1 or 2 GB) MP3 player?
The files were originally downloaded as non-copyright MIDI files from the Internet and converted to MP3 format using Sony Acid Pro 6.0. I am using a Compaq Presario M2000 laptop using Windows XP Home Edition with Service Pack.