Have you ever found the mouse has stopped and you wonder "has my computer just crashed?". I have a simple but quite effective test for you!
If you ever find that your computer has locked up or frozen the best way to test what is really going it to press the numlock button once.
If the computer has truly crashed the numlock will not turn on (or off - it toggles). It will stay the same. If the numlock light takes a few seconds (say 5-30) you know the computer is still running but it's going really slow. If it toggles immediately, or quickly, then the computer is operating fine and perhaps there is something else wrong such as a dead battery in your wireless mouse.
The reason this simple test works so well, is that the computer keep communication open to the keyboard without a lot of difficulty, so even if it's really struggling to process something, it will still respond to requests to toggle the numlock.
Note: on some laptops the number lock can be difficult to see or there may be no LED light at all! If you have a desktop PC the numlock is on the keyboard and is usually bright and shiny.
So next time your computer or laptop locks up or you think it might have, try the numlock test!