My Dell Latitude D820 has many problems.... The biggest one is that I came home from work to turn it on, and the screen is black... When it turns on, it is completely white. I am so upset! I just got this computer. My other problem is that the bottom of this laptop gets so hot! The keys and the bottom that it sits on gets hot very fast! And it does not stay on unless it is plug in. It's very upsetting, please help!

Screen issue:
It sounds like either the lcd screen or video card inside the computer is bad. To isolate the problem try connecting an external monitor to the laptop. It can be any kind of monitor even the old big fat crt monitors as long as it has a vga cable to connect to your computer's vga port. If the external monitor displays ok that proves your video card is ok and your lcd screen is the problem. If the external monitor displays the black or white screen like your lcd screen then your video card inside the computer is bad. The video will show on most systems when you reboot without you having to do anything. Some systems will require you to hit the FN (Function key) + F1 thru F12. Hold down the FN key then hit the correct key for displaying on the monitor (F1 thru F12). The correct key will normally have CRT/LCD on it or it will have the icon of a display.

Laptop hot:

Some laptops and the ac adapter get very hot. If the laptop is not shutting down, then it is not overheating, so don't worry about it. You can buy a laptop cooling pad that has fans on it and it plugs into one of the usb ports on the laptop. The laptop sits on it to keep cooler.

Your battery is probably dead so that is why you can only power it up using the ac adapter power cord. Once the power cord is removed, the laptop will turn off. Batteries only have a useful life, and after that, they have to be replaced.