When I try to add text to an existing document it erases the existing text as
I type. I've tried to turn off all auto corrections.
Press the Insert key (again, since this is what caused the behavior)
to toggle off Overtype mode.
Watch the letters OVR on the status bar at the bottom of the Word
window. When they're black, you're in Overtype mode; when they're gray
you're in Insert mode. You can also change modes by double-clicking
the letters.
If you can't be careful enough to avoid hitting the Insert key by
accident, you can disable it. In the Tools > Customize dialog, click
the Keyboard button. In the next dialog, select All Commands from the
Categories list, then select Overtype from the Commands list. Click
the word "Insert" in the Current Keys box and click the Remove button,
then click Close. (Double-clicking OVR in the status bar will still
work.)
Note that there's an option in Tools > Options > Edit to "Use INS for
paste" that Microsoft stuck in there partly because of complaints
about unintentional Overtype. I would hate this just as much -- having
whatever was on the clipboard suddenly inserted when I intended to hit
the Delete or Home key. It's better just to leave Insert as a dead
key.
