Missing music on MP3 player!

[pythia]

So I have a 4GB MP3 player, it's small but it's always served me well, but recently I connected it to the USB port in the car and I noticed that I could only view about 30% of the songs. Then, after disconnecting it, I couldn't listen to anything because a song would start playing and then freeze. When I checked on a computer I discovered that the other 70% of music has seemingly vanished, or somehow been converted into mysterious files with no file extension and I can't open them with any program on my computer. The file names are really strange-looking symbols as well. I'm pretty sure those files are what became of the missing music - one is 2GB! - but I don't know how to retrieve them. Has anyone experienced something like this before, or does anyone have any ideas how to fix it? I can get a new music player, but I'm just really annoyed.