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For some reason that website wouldn't load for me but I put the error message into Google (something I could've tried earlier - duh!) and found out how to fix it!!
Problem was that my player came pre-loaded with a load of rubbish music so I formatted it (which seemed like a good idea anyway) to get rid of it all but when I did this the root folder got deleted. I was transerring all my files to the actual player without a root file, and of course it can only hold so much without one. So created a subfolder, put all the music in there, and presto! It works!
Thanks for your help :)