Can anyone try and explain this?

I can have a document open and already typed up; if I go back through it to edit it, instead of the characters being 'pushed along ' either by the space bar or by the letters inserted pushing them along to accomodate the inserted ones, the charaters instead get wiped off ; as I move the characters with the space bar, they get wiped off instead of moved along

I hope that makes sense more than 'clear as mud'

but can anyone hazzard a guess as to why this happens?

Step 4:
Add text by moving the cursor to where you want the new text and begin typing, pushing the existing text to the side. If you want to erase the old words as you type the new, press the "Insert" key on your keyboard. You can toggle between the two choices; when you are in overwrite mode the "OVR" in the status bar at the bottom of the screen will be highlighted. Another option is to highlight the text you want to delete and begin typing. The text will be erased automatically.

Sticky "Insert" key?

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