To enable the Shell through the GUI refer to the following screenshot:
Once in the shell, login through an SSH client such as Putty.
Navigate to the location in your VMware datastore in which you wish to rename the VMDK using the following command:
cd "/vmfs/volumes/Datastore Name/Directory Name/"
Use the following command to rename the virtual machine:
vmkfstools -E examplevm.vmdk examplevm-renamed.vmdk