I don't know what that means (eg. Windows doesn't show it, throws an (error) message?), but if it contains important data you can try recovering that with iRecover.
The drive shows up in file manager but cannot be opened.
Doesn't really matter since it's not the currently used OS - scrapped now
More importantly I got my system up running again after quite a struggle which involved, disconnecting all drives except the "win2008r2 OS-drive", using the recovery console on the Windows setup disk, reconstructing the Bootmgr and finnally running a utility on the setup disk that do a "startup reparation".
It's seems there was some kind of data corruption on this drive not detected by DP. But all's well that end well!