Over time the ball picks up and transfers dust, dirt and old eraser bits to the rollers. Eventually all the dirt and debris builds up on the rollers until it forms a hard band all the way around them. When these bands of dust and dirt get big enough, they cause the rollers to slip as the ball moves, which can make your cursor do funny things.
Cleaning your mouse is very easy to do!
Removing the Track Ball
The ball we talked about is held in place by a circular cover that either slides or spins off. Take a close look at this cover. There is usually some marking or text on it that indicate which way to get the cover off. Once you get the cover off, slowly turn the mouse over and the little ball will roll out.
Wipe the ball with a moist clean cloth. Put it and the cover back after cleaning the rollers.
Cleaning the Rollers
Now that the ball is out, look inside and you will see two large rollers (these need cleaning), and a smaller one, which doesn't. The small roller is there to push the ball against the other rollers. You don't have to do anything with it.
The next task is to find a small relatively hard object to clean the rollers. A toothpick or Q-tip will work. Pretty much anything that is small, stiff and not too sharp. You don't want to scratch the rollers!
Begin with one of the rollers and scrape the ring of dirt off in a motition in line with the axis of the roller. As you get the dirt off in one spot, spin the roller a little and work on the next spot until you've gone all the way around and the ring has been completely removed.
When both rollers are clean, hold the mouse upside down and shake out all the dirt that you removed from the rollers. You may have to blow a little air in there to get it all. Don't leave any in there, because it will soon find it's way back to one of the rollers!
With the mouse upside down, put the ball back in. Then slide or turn the cover (depending on how it came off) back into place.
Don't Forget Your Mouse Pad
Before you start using your mouse again, make sure your mouse pad is clean. It is a good idea to clean your mouse pad often to keep dirt and erasure debris from finding it's way onto the rollers.