Dell Desktop Not Booting

If you can try connect to the computer in RDP... and if is possible try do windows update and update bios, firmware and driver in the rdp session

Can you boot with a bootable CD or USB.  Dell has bootable USB diagnostics so far as I know. Boot with something external and see if the hardware (minus the hard drive) runs OK.

explorer isn't starting... hit ctrl-alt-del, when the security options come up select task manager and from there file run new task and type in explorer (don't check the box) now you can investigate further.

how many video subsystems do you have?
is it just the onboard video,  or do you have another video card installed?

Can you press F2 repeatedly on bootup to get into the bios?

if you do have a secondary video card installed in the computer, can you remove that second card and hook up the video cable connector to the on board video?

I agree with Rob. I was wondering if it is booting on an external screen it thinks it has? What do you see if you right-click on the black area? I'm wondering if you can get to monitor settings (screen resolution) to "disable" the second monitor.

So does anything appear if you right click? If yes, go to screen resolution and see if a dialog appears.  If not, then David's suggestion is a good next step.

I don't have a secondary display. I pressed Ctrl Alt Del five hours ago and the menu still has not shown up.

Try rebooting the computer, and enter safemode by continually tapping the F8 key as the computer reboots. It may be a corrupted video driver and booting into safe modem will load basic generic drivers, then you can find out which devices in device manager are not installed properly.

try a repair install :  http://www.eightforums.com/tutorials/26095-repair-install-windows-8-a.html      Repair Install

Does it start with a bootable device? and can you check hardware (Dell Diagnostics)?

I don't have a secondary display. I pressed Ctrl Alt Del five hours ago and the menu still has not shown up.

To be clear, not that you have a secondary display, but that the machine thinks you have one. (Screwed up info somewhere.) in that case, you probably would not see the CTRL-ALT-DEL dialog either. I just wanted you to try a right-click on the black area and see if you get the desktop menu where you can look and see if the system thinks you have a secondary monitor. You can also look to see if the screen parameters are all wrong as well.

But I am guessing at this point that the system is not booting properly and completely.  So I would go with web-tracker’s suggestion next. See if you can boot into safe mode or one of the other debug modes.

Do you try connect to the system via Remote Desktop?

Since you did change your drivers before this happened the problem is most likely a driver issue boot into safemode then do a system restore to restore your computer to a point in time before you made changes to your drivers. If you dont have a restore point to go back to, you can check the device manager to see which drivers need updating, most likely the video drivers since you get just a black screen