Gene wrote:

I don't know if there is a specified time, but if you hold the power button long enough, power will be cut to the machine.  I only do it if all the ways I
know to perform a shut down or restart fail. 

Every ATX or newer motherboard I have heard of in the last 20 or so years, maybe longer, has supported the option to hold the power button for five seconds, which cuts power no matter what the operating system (any operating system) has to say about it.

That is a violent powerdown, and should only be done when there are no other options. The Windows boot loader, especially in recent years for some reason, has had a tendency to lose its little mind randomly after an unexpected power off event.

That is not the same as the 20, 30, or 40 second power button holds, discussed elsewhere in this thread. Those are specific to laptops, and do brand-defined things that you should only ever do in the event of serious battery or non-power-up issues. As opposed to the five second hold, which works on all PC hardware, and cuts power to the CPU and other mechanisms. Even that, as I said above and Brian has said, should be an absolute last resort. It's the same as pulling the plug on a desktop.

Luke