When you tap the Insert key, do you see OVR on the status bar toggling
between black and gray?
If not, then make sure that Tools - Options - Use the INS for paste is not
enabled.
You can double-click OVR on the status bar to toggle overstrike mode on/off.
If it turns out that the Insert key isn't doing anything at all, you can
reassign it as follows:
1. Press Ctrl+Alt+plus sign on number pad. This changes the mouse pointer to
a cloverleaf pattern.
2. Double-click the OVR indicator on the Status bar. This will cause the
Customize Keyboard dialog to appear.
3. Click in the Press new shortcut key box, and press the Insert key.
4. Click Assign, then click Close.
