1. Check the Cable Connections First
2. Look in the back of the computer and push the cables in very gently. Sometimes it helps to actually unplug them from the computer and then re-plug. You could short out the motherboard by plugging in some cables while your system is running. Shut down the machine before re plugging your mouse, keyboard, and other cables.
3. Check your power strip connection. Is it plugged into the wall? Is the power indicator light lit? Try plugging something else into that socket to see if the outlet works.
4. Look in the back of the monitor and gently push in the cables. There are usually two of them. Check both cables, the power connection and the video connection.
5. If you have a Delta Scan or TV link, or other hardware that connects to the computer, check the cable connections there also.

More coming soon !!!!!!