When I removed all my music from my coby mp3 player (MP705-4G) I went back on my coby then there were still some music on it, and i'm not sure what to do. Is there a solution?

I was able to solve this problem on my Coby MP-705 by changing the USB mode from Auto to MSC. Go to Setup/System/USB Mode to do this.
After I did this I was able to see all the missing files in Explorer.

Plug the coby mp3 player into your computer go to computer from startup and right click and format (quick).

Hope that helps.

Try this solution:

Hook up your mp3 player to your computer
Go to your desktop and double left click on "My Computer"
When it opens you will see listing that says "Devices with Removal Storage" your mp3 player should be listed there.
Right click on your mp3 player, and a window will open, right click on "Open" and now your files/songs should be visible.
Hold the left click down and drag it across all the files/songs that you do not want this will highlight the files/songs you do not want, release, right click and then click on "Delete"
Now you mp3 player should be clear of the files/songs you do not want.
Good Luck,
I hope this helps