Normally it sits between the Ctrl and Alt key. If you do not have this key, then you have an XT keyboard and need to upgrade to a new keyboard. It is generally located at the top right of your keyboard, next to the Scroll Lock key. As soon as you press this key, let go of both keys. Up pops the System Properties Menu.
Conflicts occasionally crop up when readers install new software, resulting in altered associations.
This is particularly the case when the previous association is preferred. Highlight the file extension you desire to change associations for. Hold down the Shift key and right-click the file. You will see a list appear showing every program installed on your computer. Left-click on the program you wish to use to open the file.