Keyboard in place of Mouse.

Use Keyboard As Mouse 

When mouse isn’t working properly , this trick can be very helpful. To activate mouse keys all you do is press Alt+Left shift key + NumLock and click OK or press enter .
Use the Numerical pad for controlling the mouse pointer.

5 is for click.                                  
+ is for double click
- for right click.

You can click on the setting button to change the Speed and various other options

On Screen Keyboard

On screen keyboard is one of the great windows feature that displays a virtual keyboard on the computer screen that allows people with mobility impairments to type data by using a pointing device or joystick..
To use it go to start-> run and type osk

But if your keyboard is not working how can you type OSK in Run ???

You can also start this application from Start -> All Programs->Accessories->Accessibility ->On Screen Keyboard