Happened several times already: PC failed to successfully shut down after issuing the command to do so. Aghast each time I got back to see the blue LED taunting me - I am still here.
Only got this machine fixed in early April and Windows is starting to act up. Somehow after a while and usually before a year, Windows always accumulate some detritus and begin to fail going to sleep mode or hibernation (still working) and starts up/shut down very slowly.
Happily for me, it still power up quickly. All those optimization measures are not helpful and I hate to reset the hard disc to factory and start again.
Thin OSes are better.