Greetings, I know this has been posted before. I have read the few KB's out there. So far, nothing has worked. I am running the latest Parallels software on the latest Mac desktop OS. I have a static Windows 10 VM of 512GB and want to increase it to 750GB. I am running this on an EXTERNAL 1TB Thunderbolt drive. I first went through the Parallels desktop settings to make the VM static. That worked. I then increased the size from 512GB to 750GB. That worked. The total size of the VM file on disk is now 805GB. Windows Explorer does NOT recognize this new size of the C: drive. I ran 'Diskpart' in CMD as administrator to extend the partition. This seems to have worked: DISKPART> list disk Disk ### Status Size Free Dyn Gpt -------- ------------- ------- ------- --- --- Disk 0 Online 750 GB 238 GB I downloaded and installed the trial version of Acronis Disk Director. I changed the size of the C: drive to 510GB and attempted to commit the action. Unfortunately, it seems Acronis will not allow me to commit since this is a trial version. I did notice one thing. Acronis shows approximately 238GB UNALLOCATED. Is this my missing disk space? How can I allocate that disk space to the C: drive? Any assistance would be much appreciated.