These commands should execute on your "GUEST" OS/Your virtual machine.
If the OS is a linux, run
dd if=/dev/zero of=/var/tmp/bigemptyfile bs=4096k ; rm /var/tmp/bigemptyfile
if the OS is windows
- Download this application http://technet.microsoft.com/en-us/sysinternals/bb897443
- Run the command below.
Change C: with your own drive letter.
sdelete.exe c: -z