Here are 16 actual error messages seen on the computer screens in Japan. 
Some are written in Haiku. I think they're better than, "Your computer has performed an illegal operation." 

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Chaos reigns within. 
Reflect, repent, and reboot. 
Order shall return. 

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Program aborting: 
Close all that you have worked on. 
You ask far too much. 

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Windows NT crashed. 
I am the Blue Screen of Death. 
No one hears your screams. 

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Yesterday it worked. 
Today it is not working. 
Windows is like that. 

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Your file was so big. 
It might be very useful. 
But now it is gone. 

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Stay the patient course. 
Of little worth is your ire. 
The network is down. 

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The Web site you seek cannot be located, but countless more exist. 

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A crash reduces your expensive computer to a simple stone. 

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Three things are certain: 
Death, taxes and lost data. 
Guess which has occurred? 

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You step in the stream, but the water has moved on. 
This page is not here. 

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Out of memory. 
We wish to hold the whole sky, But we never will. 

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Having been erased, The document you're seeking must now be retyped. 

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Serious error. 
All shortcuts have disappeared. 

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Screen. 

Mind. 

Both are blank