Why can’t I expand the provisioned size of a hard disk for a virtual machine on ESXi/ESX?

After noticing that I get asked:

Why can’t I expand the provisioned size of a hard disk for a virtual machine on ESXi/ESX?

… by clients on an average of twice a month, I thought perhaps I should write a post about this which includes instructions on how to fix this so I can point people to it in the future.

Problem

You would like to expand a hard disk for a virtual machine so you right-click on the virtual machine and choose edit settings:

The properties of that virtual machine open, you navigate to the hard disk you would like to expand/increase drive space but notice that all the fields are grayed out:

Solution

One of the reasons why the options are grayed out is because the virtual machine has snapshots taken of it. To check, right-click on the virtual machine, select snapshot then snapshot manager.

Once the Snapshot Manager window opens, you’ll be able to see there are snapshots for this virtual machine. In the case of the screenshot below, there’s currently one snapshot named Test created.

Select the snapshot Test and choose Delete to commit the delta to the virtual machine.

Once you’ve deleted the snapshot, you will now notice that you can edit the Provisioned Size fields in the virtual machine settings: