I have Hyper-V running on a Windows 8 laptop. Within Hyper-V is a Windows 7 Pro virtual machine for test purpose. Everything was working fine until I mounted the VHD file using Disk Management so I can browse the virtual drive in Windows Explorer. I didn’t make any changes and then just dismounted it. Afterwards when I tried to turn on the virtual machine I got an error saying “The chain of virtual hard disks is inaccessible. There was an error opening a virtual hard disk further up the chain“.

This should be a known issue with Hyper-V and we can reproduce the error by doing the same things with one of your .vhdx file. Here is how I fix the error:

1. In the Hyper-V Manager, right-click on the problematic virtual machine and select Settings.

   

2. The Settings dialog for the VM will appear. Under IDE Controller 0, select the Hard Drive. Click on Inspect on your virtual hard disk.

   

3. In the Virtual Hard Disk Properties, you’ll see the error which prevents your VM from powering on. Click Reconnect button.

   

4. When the Edit Virtual Hard Disk Wizard appears, click on Next.

   

5. Click the Browse button and locate the VHD file for your Hyper-V VM. Check the Ignore ID mismatch checkbox, then click Next.

   

6. Click on Finish.

   

   This should fix your problem. I hope this helps you out if you run into the same problem.