copy contents of C:\Program Files\WindowsApps\CanonicalGroupLimited.UbuntuonWindows_1604.2017.922.0_x64__79rhkp1fndgsc to another directory (I copied to C:\Ubuntu); Windows Explorer didn't let me browse this directory so I used Total Commander (Run As Administrator) to access it and copy
start ubuntu.exe from the new location and it should install
use ubuntu.exe from the new location going forward to start up bash etc.