How can I make NT powerdown on shutdown?

A. Follow the procedures below:

You will need an ATX power supply and an updated HAL.DLL from the computermanufacturer in order for this to work, otherwise the machine will just reboot.

Windows NT 4.0 Service Pack 4 and above ships with a file, HAL.DLL.SOFTEX which workson many systems. 

To obtain the hal.dll.softex (and halmps.dll.softex for multiprocessorsystems) run the service pack executable of the service pack youactually have installed with the command line parameter /X . This will extractall the files in the service pack to a temporary directory without installingthem. You'll find hal.dll.softex and halmps.dll.softex among the extractedfiles.

To install perform the following:

C:> cd %systemroot%system32
C:WINNTsystem32> rename hal.dll hal.old
C:WINNTsystem32> copy g:i386hal.dll.softex hal.dll

Reboot.

An alternative to renaming hal.dll would be to add option /hal=filename.extin "boot.ini".

Another file, halmps.dll.softex, is shipped for multi processor systems.Some people have reported that after using the softex dll's the CPU miss theidle loop's and this stay at higher temperatures so you may want to watch outfor this.  If you purchase Softex NT Power Management v2.19 and install itthe same happens on a Dell Inspiron 3500 Laptop with Mobile Celeron 366.

Softex have a newer version of the HAL.DLL version 4.0.1381.5 which fixes theCPU idle problem. You can download this from http://support.dell.com/filelib/download/index.asp?fileid=1981&libid=7I believe.

Windows 2000 includes better support for ACPI.