Reclaim space from your Virtual Hard Disk on VMware Workstation

I am running a Windows7 VM on a 120GB SSD, and I am running it for Internet and converting video files.  One day I noticed that the disk is about to fill up, but hang on the usage only show 70GB of usage, where is the 50GB gone??

Then I realised that it is similar to its brother software VMware vSphere, it needs to manually claim the spaces back, however in a much easier way.

I am running VMware Workstation 9, and here is the link to it’s official explanation

Select the virtual machine in the library.
From the menu bar, select VM > Manage > Clean Up Disks.

Workstation calculates how much space can be reclaimed, and either the Clean Up Now button becomes available or a message appears, explaining why the command is unavailable.

Click Clean Up Now to start the process.

A dialog box reports the progress of the clean-up process.

Once after the clean up, my host shows 70GB of usage, plenty of free spaces left again.