What damage will powering down instead of shutting down do?

"It's unlikely that the whole machine will die, but if there's anything still in file write buffers, you'll lose that data... and basically the machine probably won't know the difference between you powering it off and it shutting down due to a power cut.

Services won't get the chance to shut themselves down cleanly. For instance, if you're running a web server, when it gets asked to shut down it may well complete any existing requests (with a timeout) rather than the connection just going away.

The ""file write buffer"" doesn't just have to be the Windows buffer, either. Again taking a web server example, the logging might be buffered so it only writes to disk every 100 requests or something similar. A clean shutdown will flush this appropriately; a hard shutdown won't.

If you have online services, a clean shutdown may sign you out of them appropriately, instead of the service thinking you could just have network problems.

Basically think of anything a system might want to do when closing down in terms of either the on-board disks or connections to other systems (such as network connections) - all of those are going to be happier when shut down properly."

In addition to all the answers above, on the machine that have a RAID on their HDD and a high IO activity, a hard poweroff will most likely interrupt HDD IO required for the RAID to function sometimes leading to HDD failure and frequently - to random data loss.

"As with pulling USB sticks out of a machine without Safely removing them first, when I'm asked this question by family or work colleagues I say that is probably won't be a problem if you accidentally do it occasionally, but don't get into the habit of it as the risk is small but a definite possibility. I've certainly seen enough corrupted drives over the years.

Oh, and I usually add ""Don't come crying to me if you ignore this advice and your hard drive/memory stick ends up corrupted"". *8')"

I found an article that makes it sound like it's not such a big deal, just that you may run into some very small issues if it was writing data to the disk or using other I/O. That shouldn't be much of a problem since you've already saved everything — though you should close programs as well. Still, a proper shutdown is probably the best way to go if you have the choice.

"What I could find:

In my experience, it has never
physically hurt my computer by
manually turning off my computer. The
only thing you have to be concerned
about is what type of programs are
running at the time your shutting it
down. If you do a force shutdown via
holding the power button down,
programs that are running won't save
any current data that they have. So
lets say your running something that
keeps logs and only saves the logs
when the program is terminated. When
you do a force shutdown, those logs
won't be saved.

I'm not positive about information
not saving when you press the power
button, like if your computer is
running fine and you press the button.
So correct me if I'm wrong. But I know
for sure that when you hold the power
button in for the 3-4 seconds, nothing
saves.... especially when your
computer is frozen.

I normally don't dare to take any risks, but that might be some ""legacy"" habit from when such things were a problem. If anybody more technical can explain WHY it's not a problem that would be awesome."