Q. Using the new Azure portal how do I make an uploaded VHD file an OS disk?
A. The new Azure portal does not currently have the ability to make an uploaded VHD file an OS disk. Instead use PowerShell to make the VHD an OS disk and therefore usable by a VM. For example:
Add-AzureDisk -DiskName 'savazudc01-OS' -MediaLocation https://savtechstoreeastus.blob.core.windows.net/vhds/savazudc01-OS.vhd -Label 'OS' -OS "Windows"