First check the cable and be sure it's securely connected to the PC and monitor. Next try booting to Safe Mode. If these don't help, get hold of a bootable DVD or CD and see if the monitor comes on when you boot from it. Bootable discs would include a Windows install disc, Windows repair disc, Ubuntu disc or flash drive, etc. If the monitor comes on with a bootable disc, you know your hardware's OK.
I have not turned on my Dell desktop in over a month. Everything turns on but then the screen is just black. There's no Dell logo, nothing. But the monitor is on and it stays like that. What can be the issue? could it be the motherboard battery? If someone can help me please I would appreciate it. Thanks.