enlarge your disk - vmware virtual disk

assumptions: the disk is system volume (i.e. there's only C:).
Also, there's no snapshot: if there's any, they should be removed for this to work as described.

1) increase virtual disk file size:
vmware-vdiskmanager -x 20Gb vmdiskfile.vmdk

2) add it as hd to another vm.
note: once the other vm has booted, the "new" hd should already automagically have a letter assigned. if not, then there's probably a snapshot and the process won't work (point 7 won't, at least).

3) inside the booted vm open a dos window and run: diskpart
4) list volume
5) set volume=X
6) list volume, just to verify
7) extend

That's it. Shutdown, remove the disk and go back to the original vm.