For some reason, Delete and Insert keys are combined on my laptop (ASUS). You have to press fn key and Delete key to get Insert.
The simple system-wide solution to this is the xmodmap utility; this utility allows you to map any key to any other key.
In my case, I decided to use Pause key instead of Insert (how often do you need the Pause key anyways?), and this is all you have to do:
xmodmap -e "keysym Pause = Insert Insert Insert Insert"
Add it to rc‘s to get this automatically run on system startup.
Note: in the xmodmap command above, the 1st Insert is a key press with no modifier pressed, 2nd with Shift, 3rd with Ctrl, 4th with Ctrl+Shift.