I am totally stumped by this and have done this many times successfully in the past.

I create a parent disk (Windows 10 build 1607, have to use this old build for testing purposes) and then a differencing disk against this parent using Hyper V using methods such as described here:



When I start the diff disk vm for the first time I get a black screen with blinking cursor.

In desperation I tried this


and it seems that no C drive is available when I go to the command prompt. This sound like it would be part of the problem (obviously).

Any ideas why this would happen? I have googled around and people have various problems with starting the vm and hitting a black screen but none of them work for me.

FYI trying to debug the issue in any way I could I found that pressing F8 (after adding the hyper v delay) during boot does not get me to any BIOS menu.

Thank you for any help m


For anyone who has a similar issue in the future I describe what worked, though I don't know why.

I was creating my parent disk on an UN-PATCHED (i.e. no updates applied) version of Win10 1607.

Recently I applied all patches (as of 28 September) to the parent disk (Windows 1607), sysprepp-ed it and created a new child diff disk: this worked.

I guess something in one of the patches must have fixed the issue? I don't really know.


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