is a power option set through the System BIOS and through the Control Panel applet. Try RE-SETTING the power options.
You mention "the day before I tried shutting it down and failed, I spilled a bit of water (less than half a cup) on my laptop while it was asleep" and that is most likely the actual fault and cause of your problem - even a single drop of water in the wrong spot is more than enough to cause problems ranging from glitches to actual arcing shorts.
I would suggest positioning the laptop so any moisture could drain from both top and bottom and set it in front of a fan blowing air from a floor heat vent for a couple of DAYS as it will take some time to dry areas that can't directly be reached.
As far as manually turning it on and forcing a manual shutdown by holding down the power button, that is how it was done before auto shutdown was available so the only damage you might see would be increased usage of the power button.
I have a Sony Vaio Z Series, Intel Core i5 2.53 Ghz 4 GB RAM on a 64-bit Windows 7 Professional.
When I try to shut it down, or make it sleep, or hibernate, it invariably **restarts** instead. The only way to shut it down is mechanically by holding the power button.
I have done everything I can think of, including: reformatted and reinstalled Windows and used HD Tune to scan my hard drive for damage. I have unchecked the option to automatically restart in case of system failure (from System and Security in the Control Panel). Before reformatting, I tried using System Restore - with 2 different dates - but each time the problem was made worse as Windows wouldn't even load (I got the BSOD). So I went into Safe Mode and undid the system restore.
One thing I should mention: the day before I tried shutting it down and failed, I spilled a bit of water (less than half a cup) on my laptop while it was asleep. I immediately took out the battery (it was unplugged), let it sit for like 13 hours, then blow dried it for a bit, and turned it on. Everything seems to work perfectly, except it won't shut down!
Any ideas? I absolutely love my laptop and spent a lot of money to buy it. Have never had any problems with it until now.
And functionally, I suppose, there are little implications: I can just manually force the shut down every time. But is this sustainable? Or will it prove to be prohibitively damaging?
I'd really appreciate any help! Thanks very much.