1. Before we begin, let’s take a look at the disk size. In my example, it is a 80GB disk.

2. Now, power down the Virtual machine so that it state is “off” in the Hyper-V Manager. After that, highlight the Virtual Machine and then click “Edit Disk…” under “Action” on the right.

3. A Edit Virtual Hard Disk Wizard window will pop-up on the screen. To continue, simple click the “Next” button.

4. Locate the Virtual Hard Disk by clicking the “Browse…” Button.

5. Once you find the correct virtual disk, highlight it and then click “Open”.

6. In the next screen, you can choose 4 different actions you can do to the virtual disk. In this example, we go with “Expand”. Click “Next” to continue.

7. Now, enter the new disk size you like you virtual disk to be expanded to. In this example, I enter “120GB” in the text box provided and click “Next”.

8. Virtual Disk expanding summary. If everything is correct, hit “Finish” to proceed.

9. Once that is done, you can start/power on the virtual machine follow by “Connect…” to the Virtual Machine console.

10. Open the Windows 8 or Windows Server 2012 search page and type computer. Once the Computer app appears on the left, right click the “Computer” and choose “Manage” at the bottom.

11. In the “Computer Management” screen, choose “Disk Management” under “Storage”. You should see the additional space listed on the screen now as Unallocated space.

12. Right click the drive/volume you like to expand and choose “Extended Volume…”

13. A Windows Extend Volume Wizard will pop-up to guide you through the drive expansion process. Click “Next” to begin.

14. Select the disk you like to expand and choose the amount of space you like to expand. Once that is done, click “Next”.

15. That should do it. Just click “Finish” to exit.

16. At this point, you should see the new size of the virtual disk inside the Disk Management screen.

17. If you open the Windows Explorer again, you should notice the changes in “Total size”.