Forcing ACPI for power off

Problem: Ubuntu 12.04 and machine wont power off
My machine is Dell Latitude D630 with NVIDIA Quadro NVS 135M

1. sudo gedit /etc/default/grub
2. Find where it says, GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
3. Change this to GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi=force"
4. sudo update-grub