You have a symptom of power light is on nothing on screen no data signal. This symptom the problem is no display. probable cause is bad ram, gpu cards or the mobo. You need to clean this parts to make it sure that it will display if there are no circuit problems. After you clean it, test it one by one in your mobo but simply connect you PSU and powerup using paper clip in front panel power pins. During test if one of the parts failed that parts is the problem you need to replace it. Be sure to not connect your HDD during testing of the display to avoid damage.