I'm trying to mount a vhdx file in windows 8.1 and it's giving-me this error:

The process cannot access the file because another process has locked a portion of the file

This file was created in a local directory and copied to NAS share.

If I try to create it directly on NAS I get the same error.

If I use (or try to create) vhd file in Windows 8.1: Same error

In Windows 7 I can create and attach the file without any problem. 

With all these problems, I cant perform System Image Backup as it creates vhd/vhdx files.

• Edited by Sandro A Silva 17 hours 27 minutes ago Correcy

Have you tried to create a new vhdx file and copy the contents to this new target?

Here is a quite similar situation like you have.

http://homeservershow.com/forums/index.php?/topic/6112-vhd-will-not-attach-in-windows-8/