Let’s say you’re going home, and shutting down your Windows-based computer for the day (Windows XP, to be specific). And after you’ve already pressed Start/Shutdown, you think “o crap”…and remember something you’ve forgotten to do.
Is there a way to get Windows to pull the emergency cord and come back up, without waiting (forever) for the shutdown / power off process to complete and rebooting?
No
No. Once you have initiated a shutdown/reboot, it’s irreversible.
If you’re *really * fast, you can open a command prompt and enter the command shutdown /l /a /y
More about the shutdown command than you ever hoped to know:
Your hypothetical is the exact reason I created the following pair of shortcuts on my Desktop.
The first is labeled “Shutdown” with the target "C:\WINDOWS\system32\shutdown.exe -s -t 10 -c “Goodnight.”. When activated, it shuts down displays a warning message and shuts down windows after a ten second countdown.
The second is labeled “Abort Shutdown” with the target "C:\WINDOWS\system32\shutdown.exe -a -c “Shutdown aborted.”. If activated during the countdown, it cancels the countdown and Windows returns to normal operation.
Not exactly what you asked for, but it works for me.
Now see, I didn’t know that. Ignorance fought, thanks.
Though I must say, you would indeed need to be fast.
If you have an unsaved document, and the “save, don’t save, cancel” dialog comes up and you click cancel, shutdown is stopped.
Heh. This is kind of funny. I had this happen just now. I had finished some stuff, selected “turn off”, and thought “oh crap, that’s right… I was going to read the Dope while eating this sandwich. I sure wish there was a way to abort the shutdown.” I wait (forever) for the computer to shut down, turn it back on, wait (forever) for Windows to start, open the Dope, and the first thing I see… is this thread.
Apart from that, I got nuttin’.
Why would you ever shut down your computer at night?
Because you don’t want your computer to be humming and heating up your cramped student room while you’re asleep there? Plus it probably uses less electricity off than on (but maybe this is offset by the energy it costs to get it up and running again? I don’t know).
I have two computers. One I use every day, and leave on overnight. The other, which is for my 3D graphics and video editing hobbies, I only turn on when I need it.
For me, it’s not to save power, it’s because the second computer has a couple of loud fans which are really annoying when I’m trying to watch TV, so I only have that computer on when I need to use it.
These made me giggle inside…
I have an older machine. When it gets sufficiently warm, the wireless card gets wonky.
I always used to shut my PC down at work before I went home. They were always harping on us about saving energy (to save money), and even installed software on all our workstations that would automatically power down the monitor if your PC was idle for more than fifteen minutes. Then, a couple years ago, they decided to install software that would automatically power up your PC at midnight every night if it was turned off, just in case they needed to push out any software updates (which they do maybe once every month or two). So now I just log off when I go home but leave the PC running, because I figure it will be back up in a few hours anyway.
In order to stick it in its bag and carry it out to the parking lot for the drive home.
Because you have to remove the (classified) hard drive and lock it up in the safe, for some people. 
I assume you’re talking about a laptop. Serious question: Does that actually require shutdown or is hibernation adequate? (What I’m really asking, I suppose, is whether or not I’m committing some Deadly Sin when I transport my laptop hibernated…)
I admitted my error. Giggle away.
Hibernation is fine if it works well for you. I almost never shut down mine - it’s either hibernate or restart (when needed for software installs or instability).
Thanks. That’s about how I operate, too.