So you want to create a Hyper-V on your Windows 8 computer to use for Server 2008/R2? I hope that reading this post can save you some time and frustration when you try to move the fresh image that took you a while to make only to find out it won’t work in Server 2008.
With the new features in Windows 8 and Server 2012 Hyper-V now has a new extension of VHDX which is not backward compatible with older systems.
If you found this too late there is no need to re-create your image as it can be converted from Server 2012 or Windows 8. This conversion also supports VHD to VHDX conversion just follow the same article and chose VHDX instead.
Open up your Hyper-V manager in Windows 8
On the right side under “Actions” select “Edit Disk”
Click Next when the edit virtual hard disk wizard comes up
Click on Browse to locate your VHDX disk you wish to convert
Once located and selected click on Next
You will now be prompted with 3 options
Now chose what version you want to convert to and in our case since we already have a VHDX we want VHD so it can be used for 2008/R2
When you initially created the virtual machine if you accidentally selected Dynamic instead of Fixed here is one way to change that. If you want to keep it the same in this case Dynamically available just click Next
Last thing is where you want to save the new file
Now confirm your settings and click on Finish
To mount this VHD just go through the New Virtual machine and when you get to the point to connect virtual hard disk just select “Use an existing virtual hard disk”.