Multiple Monitor Blackout

So you've got several monitors plugged in various ways to your computer, something happens or changes, and now when you boot up you may or may not see the Windows XP booting bar but after that you have black screens, or even more frustrating, you see blue or a wallpaper and a mouse but no login screen, desktop, or taskbar.

STEP 1: First and foremost, try the stupid thing first.
Reach back there and move one of the monitor cables to any unoccupied VGA or DVI ports and see if you get what you need. If you're lucky you'll find where your primary screen got sent and be able to juggle the monitor settings.

If you have no luck with that, keep going

Step 2: Second, the tedious and frustrating part.
Begin moving cables around and rebooting the computer until you find the BIOS, watching for what key your particular BIOS uses to open up the setup menu. Once the BIOS comes up your going to want to look for a section pertaining to VIDEO and then something like Primary Video. This menu should have an Auto setting and an Onboard setting. Dell BIOS has Auto set to default to your graphics card, while Onboard defaults to the motherboard VGA port UNLESS a PCI card is installed. Here's where you get complications, but go ahead and set your BIOS to whatever Onboard setting it has, save the changes and exit.

STEP 3: Almost done.
Power down the computer and look at your PCI/AGP card positioning. Whichever one is positioned closest (assuming you have multiple graphics cards) to the top of the openings is going to have a "higher" addressing as far as the computer cares (keep in mind you're motherboard might have the lowest slot as the highest address, the only thing that is guaranteed is the highest address is at the top or bottom of the rows of ports). Make sure something is plugged in to one or all of the ports on that card and startup the computer. Also make sure a monitor is plugged into the motherboards VGA port if you can.

Step 4: Configuration and the end of the problem
By now you should have your primary output visible on at least one of your monitors, but before we go setting up the monitors, make sure you have the latest versions of your graphics card's software suite (either ATI Catalyst or nVidia Control Panel). If you do download and install either of these then reboot once more.
Now you can proceed as normal with logging/booting XP and then setting up your monitors as you like using either the Windows monitor settings or your graphics cards software suite.

If you're still having problems, open up your case and remove your graphics cards completely, rebooting with a monitor plugged into the motherboard VGA port and nothing else.

If all else fails, you've got more serious problems or something very simple but overlooked.