That's exactly what I thought. Some audio went AWOL then some instruments turned up but are now forever muted. I'm hesitant to use folders again.

AFAIK, the only way audio would go missing would be if you did a "Save As" to another location and neglected to check "Copy audio With Project"
 
Either that or the files were deleted via Windows Explorer

Could you not use Windows 7+ Libraries to achive this?

Bristol no I didn't save as that would be ridiculous not only did some audio go missing but as I said some plug ins stopped working on those particular tracks, I am on windows 8.1 Kperry. It's obvious windows is not working out plus Windows folders are dated it needs an overall!!!