Please try to perform the following steps;
And we also strongly recommend that you make a backup of the virtual machine before following the troubleshooting steps.
In Mac OS X, open Finder, go to Applications folder > Utilities folder, and double-click Terminal.
Paste the command below into Terminal as is (do not hit Enter yet):
prl_disk_tool check --hdd
Find your virtual machine in Finder. Right-click on the .pvm file of your virtual machine and choose Show Package Contents
Drag your WindowsXXX.hdd file into Terminal and drop it right next to prl_disk_tool check --hdd.
So as result you will see something like this in Terminal window: