A Microsoft employee recently contacted us with this issue:
“When I try and attach a virtual hard disk to a generation 2 virtual machine – I get an error message that says ‘Error applying Hard Drive changes’”
It took a bit of conversation – but eventually we figured out what was happening. Here is the error message in action:
What is happening here? The answer is that we only support .VHDX files with generation 2 virtual machines. You cannot attach a .VHD file to a generation 2 virtual machine – and if you try to do so you will get the error message above.
If you have a .VHD file that you want to connect to a generation 2 virtual machine, you should convert it to a .VHDX first.