My Nikon D40's manual mode doesn't work?

I just bought it 15 minutes ago off of craigslist.
it works in all modes except manual, on the screen it just shows up black.

also it says that flash is on but it doesn't flash.

i've never used a dslr so i don't know exactly what i'm doing.

Added (1). Let me extend the previous information.

in manual mode, the picture after it's taken doesn't show up on the screen like it should in normal DSLR cameras.pick up a manual.

I don't know how Nikons work, but on my Sony camera unless you are in full automatic mode you have to press the flash button to make the flash pop up even if it says the flash is on. Is the screen showing up black or is it black with the settings on it? I'm not sure if the D40 has live view. Look in your viewfinder and snap a picture and see if one turned out.

If the picture just isn't showing up on the screen it's not set to do that or it's not capable of doing that either one. With my camera you can set it to show your images right after they are taken or you can turn that off. There's a playback button just press it to view your photos. You need to read the user manual.

Uh, yeah, in manual mode YOU have to adjust the shutter speed and aperture. Go to your local library and read some basic photography books. Update - You just have to press the "play" button after you take a picture… No biggie…

In manual mode you have to set the aperture, shutter speed, iso, etc.
It's coming out black because there's not enough light. Either make the aperture larger (which is smaller in number.f/1.8 is larger than f/2.8), make the shutter speed longer, higher iso, or balance all three out until you get what you want.
You can go online and print out a cheat sheet with all the settings for difference requirements on them. That will help you out a lot since you're a beginner.

Set camera to A mode and go out, look for a brightly colored car parked under the sun and take its picture. If the picture does not come out in the LCD automatically, press the preview button (the triangle pointing to the right). If still there's no picture, make sure there's a memory card installed (turn off power first). If everything seems to be all right, the camera may be broken. If not, you just didn't use the right settings in M mode to get a properly exposed shot.