How will you click on the icons or do something with your mouse, if your mouse if not working ? The solution is to use your keyboard keys to control the mouse pointer. All you need to do is enable the mouse keys by going into the settings. If you are using windows XP, 

1. Click on start button
2. Go to settings
3. Go to control panel
4. Open accessibility options
5. Click on mouse tab
6. And check the box saying ” Use mouse keys “

Once you do that, you will see an icon in the system tray showing that the mouse keys are enabled. Now what you need to do is to use the number pad on your keyboard to control the pointer. You need to turn the numlock on and then use 2 for moving the cursor down, 4 to move the cursor to the left, 6 to move the cursor to the right, 8 to move the cursor up. Use 5 to left click. 

The settings to turn the mouse keys on in Vista is a little bit different. 

1. Launch the start menu. On the search panel type “ease of access”
2. Click on “make the mouse easier to use” button
3. Check the box saying “Use the mouse keys”
4. Press save button and apply.

Everything else is the same as in XP.