yeah i get that message too, bit odd as there is no mention of it in the tutorial, i think i will message the tutorial writer to ask. try the repair utility fix and see if that helps.
Fix & Repair Windows Media Player with Fix WMP Utility
though it will clash with the windows codecs you installed as i just discovered, resseting the codecs back to sharks reccomended settings worked.
also have you tried the sfc scan i mentioned a couple of posts ago.