Enabling Automatic Shutdown on Compaqs

In our company our users have mostly Compaq machines. They are Deskpros and a few Prosignia Desktops. I would like the machines to turn themselves off automatically when the user chooses the shutdown option. I have been successful on most of the deskpros by going into the BIOS and enabling the advanced power management but when I do the same for the Prosignia’s they stay at the screen that says you can now shut down. How can I get the prosignias to turn themselves off?