Would that be a Demension 5100?
If it is there are 4 Diagnostic Lights that light up 1-4 on the front panel by the USB ports are any lit?
Again if it is a 5100 it can mean a Power Supply or system board(motherboard) failure sometimes a CMOS clear will get it running again> http://support.dell.com/support/edocs/systems/dim5100/en/sm/setup1.htm#wp1097561
If it is there are 4 Diagnostic Lights that light up 1-4 on the front panel by the USB ports are any lit?
Again if it is a 5100 it can mean a Power Supply or system board(motherboard) failure sometimes a CMOS clear will get it running again> http://support.dell.com/support/edocs/systems/dim5100/en/sm/setup1.htm#wp1097561