Cars have idiot lights that come on to tell you when it is too late to change your oil. My computer could use one of those. What it does instead is start giving off a loud buzz/hum when I have been an idiot and let its coolant levels drop too low. It caused me concern and it scared the cat.
I'll have to keep a closer eye on this thing so that I can top it up before it's down to sucking on air again.