The five signs a computer has locked up:
It doesn't respond.
It doesn't respond.
It doesn't respond.
It doesn't respond.
It doesn't respond.
suffice to say that, when in windows, you can't get the task manager open (and deal with whatever problem from there), it's time for a hard reset. You may be able to slide the cursor back and forth 'til the cows come home, yet clicking on anything yields no response.
This is what I mean by "The computer has stopped responding".
On very rare occasions (and usually in linux or os x), a usb keyboard (and anything daisy-chained to it) will stop working until I unplug and re-plug it.
I've also seen hdd lights continue intermittent blinking for long periods after a pc has hard-locked. I wouldn't say the lights are completely useless, but by the same token they aren't completely reliable, and certainly not essential.
And who are you being rude to on the phone, by reading and answering forum posts while they drone endlessly on about something you have no interest in?
Your mom?
I'm with the LED gang. I'm always using hard drive indicator lights at work to make sure computers are getting all of their network-sent msi packages fired at them, purely because they all run totally hidden.
Helen's Dell XPS 15 has a hard drive indicator light on the back of it. So anyone watching her use it can see the hard drive working, but she can't while using it. Seems pretty stupid if you ask me.