|First off, verify you are connecting the monitor to the correct port. If still no go, then open the case and re-seat all cards, RAM, & cables. Some thing may have worked loose. |
Be sure to discharge yourself or wear a ground strap. You can simply touch the metal case before unplugging it. While you have it open, it is a good idea to blow out all the dust/dirt. You can use canned air or a compressor. DO NOT use a vacuum cleaner because static created in the hose can damage sensitive components. You may want to move the tower outside because there will be lots of dust. Be sure to also blow out the power supply from both ends.