The other night, I went to play some of my favourite music on Windows Media Player. It couldn't detect ANY of the songs I wanted.
Being a suspicious old sod, I interrogated my sons to ask if they'd removed my music for some reason. They all denied having done so.
Going into the folder that I keep all the family's music in, I discovered that the songs were there, but that they had suddenly acquired the file extension of .M4a, rather than the .MP3 format they were originally stored as.
Upon investigation, I discovered that the new file type is used by iTunes, which I'd downloaded some time ago. How and why the iTunes program decided to change these particular files from .MP3 to .M4a, I haven't a clue! Point is, WMP doesn't recognise .M4a files, so excludes them from the library!
I insist in using WMP for all my music activities on my PC and I am rather angry that a program like iTunes can change files as it sees fit - I certainly did nothing to change the defaults myself.
To resolve the problem, I had to download a utility from the net that changes audio file formats (it's called "Switch" from NCH Swift Sound). Having converted the .M4a files back to .MP3, I then had to do a lot of editing in WMP to restore all the titles to the library in the manner I am used to.
I have accordingly removed iTunes from my PC and am about to send Apple an appropriately worded email to tell them what I think of their software!