Thanks, but,,,
Went into /control panel/Storage/Disk Manager/. Found the drive that does not
have drive letter assigned.
Tried to assign, the default was "H" which is the next letter of all used.
The message box said something like "This letter is used. Reset the letter anyway?"
Did it, but it was rejected.
My next option was to assign "I". the Response was "Invalid parameter".
There seems no way to give a letter.