It sounds like your windows install has become corrupted. Hence the loss of Start8.
The message will come from Windows and is nothing to do with Start8 itself. It means the OS has corrupted your documents and pictures library entries. The good news is your physical files are ok, it is just the library which merges mydocs + shared docs is corrupted.
I would check your Hard drive for errors as it may be failing. Either that or did you have to turn the machine off without shutting down recently?
