Dude... Â the installation instructions that we pointed you to earlier explicitly say exactly that the System folder is a 'hidden' folder and you need to make the hidden folders visible before you see them .. Â Â I thought you'd said you'd read the instructions, but all the problems you had were because you missed parts of those instructions out.
If the instructions are not clear, could you pls let us know how to make them clearer? This will help other users in the future.
As for whether rockbox can only play mp3s .. Â Â short answer is no, it can play other things too, but
read the manual. Â I'm not going to tell you which formats rockbox can play because it's
all in the manual. Â Every question you probably have about rockbox is already answered in
the rockbox manual. Â Hopefully that's clear now Â