When a Windows virtual machine runs low on hard drive space, be it the primary C: partition or a separate data partition, both the hard drive and the partition must be extended in a proper manner. This requires the use of both the VMware vSphere Client and using the DISKPART command-line utility. This document only covers the proper use of the DISKPART utility.
Once the appropriate virtual machine hard drive has been extended through the VMware vSphere Client, log on to the Windows virtual machine with an administrative account and bring up a command prompt window, then run “DISKPART”.
Once DISKPART has started, you will want to tell it to re-scan all of the drives and detect any new changes by running the “rescan” command. Once it has picked up on any changes, you can get a list of drives by running “list disk” and select the appropriate drive that has just been extended through vSphere Client by running “select disk x” (replacing “x” with the appropriate number in the “list disk” command output).
Next, you will need to list the partitions on that drive by running “list partition” and note the partition number that needs to be extended. Select the partition by running “select partition x”, again replacing “x” with the appropriate partition number. To extend the partition and the file system it contains, simply run “extend”. Once extended, the new file system size should be reflected in Windows Explorer and in Disk Management. Use the “exit” command to exit out of DISKPART.