BE Error message - need help

[BkExNewbie]

I have this error message

"Exact Error Message
V-79-57344-34033 - The media in the storage device was changed "

The backup runs at 8:10 pm. no-one was here to change the media. What else could this mean?

The error message says to: "check the System Event Viewer Log for the hardware related events." How do I do this?

Here is the link to the error message. I would appreciate your help. Thanks