Okay so I assuming you know how to load a live linux CD in a VM and in a Physical computer. If not email me and I will add these instructions for you.
1. REboot the machine and press the key either it be F12 F2 ESC to get to the boot menu.
2. Select to boot from CD
3. Once the OS has loaded open up the Terminal and make sure you have root access.( you probably will since its a live linux cd)
4. Make a temporary directory to mount the local HDD:
a. mkdia /a
5. Now Mount your local HDD to the temporary directory.
a. mount /dev/sda1 /a
6. Now remove the hash value for the account you forgot the password for in this location /a/etc/shadow
a. nano /a/etc/shadow
b.example: root:(remove the contents between these colons):11111:0:99999:7:::
7. Unmount /a and disable or remove the iso or cd for the live linux OS.
a. unmount /a
b. sync; init 0
c. remove the CD or disable the iso in the VM settings and reboot
8. You should now be able to log into the OS with no password
if you want to change your password via the terminal which i think is easier run this command:
username = the username account password you want to change
***If you need a live linux CD Hirens Boot CD has a linux and a windows that loads into the ram or you could download knoppix or bt5***