By default in Microsoft Word, when you hit insert key, Word jumps into overtype mode, which writes over the text at the cursor instead of inserting new characters. This drives many people insane. The fact that it is a default behaviour remains to be seen.
How to fix overtype mode:
There are two options to remedy this:
1. Go to Tools > Options > Edit > Overtype Mode
And uncheck the Overtype mode box.
2. Kill the Insert Key:
1. Start Word
2. Click on the Tools menu
3. Click Customize
4. Click the Options tab
5. Click Keyboard
6. Under the Categories dropdown box, select All Commands
7. Under the Commands dropdown box, select Overtype
8. Under the Current keys downdown box, select Insert
9. Click Remove
10. Click Close until the dialog windows close.
Thanks to the guys at tech-recipes.com, where I discovered this information after years of using method 1! this guy deserves a medal!