Can anyone tell me why all my books have gone from Calibre? They were there when I closed down my computer and not there when I reopened it a few days later. I had over 3000 books and now all links show 0 books.

panicking here.
PS: ok found the Calibre Library in my E drive but Calibre is trying to find it in C drive and that drive is full. so must have migrated it to E???? How do I get Calibre to see it in E drive now?