You are using PE to create VDisk to C
You are using windows C to test for programdata
Use Diskpart in Ram X to determine Drive Letter for the OS partition, as most likely not assigned C
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Diskpart
List volume
Verify drive letter assignment of OS Partition - change vdisk command accordingly
Kyhi makes a good point. the LIST VOLUME command in Diskpart may help you find the correct letter to use.
So, one could assume you trying to create a "Windows Server 2019" Virtual Disk that will run from a USB ???
You do realize that the USB Media will be real slow running the VHD and may not even work due to removable media flag....
You could create an expandable VHD/VHDX on the Root of your C drive - Apply the WS2019 Install.wim Image to the VHD and then add the VHD Boot Menu Entry into your Hosts Boot Menu options
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