This can happen if you had an external hard drive or thumb drive installed
which was assigned a drive letter then removed and a different piece of
hardware, like a card reader, assigned the same drive letter. I don't why
this sometimes happens, but for whatever reason the original piece of
hardware didn't uninstall properly, leaving Windows to continue to look for
that piece of hardware. So, for example, if you'd originally had an external
hard drive installed and assigned drive letter "d:" then it was removed and
your card reader then installed, taking over as drive "d:" then Windows would
be expecting a hard drive, only to find no drive (empty card reader). I've
found it can be resolved by uninstalling whatever external drive you have,
rebooting, installing the drives, one at a time, rebooting each time in
between each install. That way each is being reassigned a new drive letter.
If for whatever reason that doesn't seem to resolve it then try going into
Computer Management --> Disk Management, then manually reassigning the
external drive a new drive letter, then rebooting.