Being able to distribute your classic Desktop App through the Windows Store is a great opportunity to target the 500M+ Windows 10 active users!
So you may be using the Desktop App Converter tool and you might have the following error since an major Windows Update:
'E_NO_EXPANDED_BASE_IMAGE': No expanded base Images were found a 'C:\ProgramData\Microsoft\Windows\Images'. Please run with -Setup to expand a new base Image.
To solve this, you just have to download the Fall Creators Update image...