how do I get my computer to shut off automatically instead of giving me the message: "it is now safe to turn off your computer"?

Use program called switchoff

Make sure you have APM (Advanced Power Mangement) enabled in your BIOS. Here are some others: In some cases, Windows XP’s Setup program can misidentify the power management scheme in a computer’s BIOS as Advanced Power Management (APM) instead of Advanced Configuration Power Interface (ACPI). When this happens, users will notice that the computer no longer automatically powers down when they shut down Windows XP. Instead, they’ll see the message It Is Now Safe To Turn Off Your Computer and they'll be forced to manually press the power button to turn off the computer. You can verify this problem by checking the power management configuration in two places—Device Manager and Control Panel. To quickly access Device Manager, select Start | Run, type Devmgmt.msc in the Open text box, and click OK. When you see the Device Manager window, locate and open the System Devices item. If Setup identified the system as having an APM-compliant BIOS, it will be listed as a Standard PC in the System Devices tree. (If it were identified as having an ACPI-compliant BIOS, you would see it listed here as a Microsoft ACPI-Compliant System.) To check the power management configuration in Control Panel, open the Control Panel from the Start menu. If the system is using Category View, select Performance And Maintenance and then click the Power Options icon. If the system is using Classic View, just click the Power Options icon. If Setup identified the system as having an APM-compliant BIOS, you’ll see an APM tab in the Power Options Properties dialog box. (If the system were identified as having an ACPI-compliant BIOS, you wouldn’t see an APM tab.) You may be able to fix this problem with a BIOS update. To begin, check with the computer manufacturer’s Web site to see if it’s providing the latest BIOS update. If you’re troubleshooting an off-brand computer, you may be on your own as far as tracking down the BIOS update. Once you obtain and install the BIOS update according to the manufacturer’s instructions, you must perform what I call a Refresh Installation, in which you reinstall Windows XP on top of an existing Windows XP installation. You must perform this reinstall operation because the power management features are tied to a special power management Hardware Abstraction Layer (HAL). During the Refresh Installation procedure, Setup will completely redetect all installed hardware, including the updated BIOS, and rebuild the power management HAL as well as the part of the registry in which information about the installed hardware is stored. This has worked on systems before as well. As always, back up your registry first: Open your registry and find the key below. Create a new string value, or modify the existing value, called PowerdownAfterShutdown and set it to "1" to power off the computer at shutdown, or "0" to reboot. Restart Windows for the change to take effect. -=Bryan=-

Goto /Start/Control Panel/Performance and Maintenance/System. Select the Hardware tab and then select Device Manager. Under 'View' menu select Show Hidden Devices. Double click NT/Apm/Legacy InterfaceNode and enable device. De-select show hidden devices again and re-boot. PC will shutdown automatically.