mech on windows does not work because tar interprets colons (:) in file names as meaning it is a file on another machine.
$ mech up
Loading metadata for box 'envimation/ubuntu-xenial-docker' (1.0.0-1510009906)
Box 'envimation/ubuntu-xenial-docker' could not be found. Attempting to download...
URL: https://vagrantcloud.com/envimation/boxes/ubuntu-xenial-docker/versions/1.0.0-1510009906/providers/vmware_desktop.box
vmware_desktop.box [################################] 169768/169768 - 00:01:46
Checking box 'envimation/ubuntu-xenial-docker' integrity...
tar: Cannot connect to C: resolve failed
Cannot find a valid box with a VMX file in it
mechon windows does not work becausetarinterprets colons(:)in file names as meaning it is a file on another machine.