Ctrl+Z, by default, undoes a single change. If your whole document
disappeared when undoing a single change, it must have been created with a
single change - a Paste, perhaps - in which case you haven't lost much work.
However, I don't know what you mean when you say you were left with a blue
screen - do you mean you had no documents left open? I don't believe thats
possible from a default Ctrl+Z action. Perhaps you could give more detail?
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Enjoy,
Tony
www.WordArticles.com