there are multiple ways to accomplish:
If you are on a licensed edition with svmotion you can just svmotion the system to another volume and slect thin provision...that will drop the actual usage down to what it uses.
You can also shut down the VM and do it as well.
You can also use vmware converter to re-copy the VM and reduce the Data Usage
You could also just add a new drive to the existing system and use robocopy to copy all the data to the new drive, then just switch the drive letters around so the new drive has the correct drive letter and then you can delete the other drive from the vm...