Nikon D40 built-in flash...

The letters you're referencing is the M/A (manual / auto) focus switch. The lens has this switch and operates in Auto Focus mode when set to "A" and manual focus mode when set to "M".

You have to manually focus on the subject when in letter "M". If you do not, the result will be out of focus. From your description, it sounds like the camera / lens combination is attempting to focus and operate the shutter in auto, and focusing in manual; but due to some type of damage resulting from possible mishandling, exposure to dust, dirt or even moisture is interfering with the successful completion of the process.

You could isolate the problem to determine if the cause is in the lens or camera by simply attaching the lens to another compatible Nikon camera or placing a different auto-focus lens on your D40. The problem will either stay with your D40 or follow the lens when attached to a different camera. It is also *possible* that due to numerous attempts of auto-focusing with your D40 & lens combination, that both the lens *and* the camera have been damaged. If the problem is severe enough, the problem in the failed device could cause failure in the otherwise normally working device, too.

You might be best served by contacting Nikon Service & Support below:

http://www.nikonusa.com/Service-And-Support/Service-And-Repair.page

You also said you lost your manual. You can download the manual for the D40 directly from Nikon in your choice of English, French or Spanish from the link below:

http://support.nikontech.com/app/answers/detail/a_id/14157/session/L3NpZC9YRTgxQVpKag%3D%3D/kw/D40%20manual/p/19%2C334/c/187/r_id/116678/sno/0

Good luck!

Turn off the flash manually (top left button on the side of the camera body above the lens) or use the 'No Flash' Program Dial option - one click back from the green AUTO selector on your dial - the one with the lightning bolt inside a circle.

Make sure you're not shooting on no-flash auto mode. Also, in P, A, and M modes you'll have to press the flash button on the side of the camera by the lens mount in order for the flash to pop up. If it's not popping on regular auto mode, make sure you don't have it disabled in the menu.

You have your camera set to RAW format. It is not a compressed file, it is a full size file. Opening this in editing programs will either crash your computer or will refuse to open because of the size of the file. They are not damaged but your computer cannot handle the files. You should take them to a photo shop and have them put the files on a cd and consult your manual to change your camera to JPEG format.

there is a sensor in there that tells the camera the flash is up you need to take it to a repair shop its not a at home thing

is it set to auto? if not i suggest you check the aperture and shutter speed setting :)

I assume the lens had the impact. The 18-55 lens has the built-in motors for auto-focus.
Try switching to manual focus (on the lens). If this works, the lens may not auto-focus anymore.
Try it and let me know.
cheers,

The lightning bolt icon in viewfinder blinks when flash is not ready, this can happen if flash doesnt pop up all the way, or if flash strobe tube is bad.

With the command dial set to "auto", try to take a shot in low light. The flash should pop up automatically. You can't manually pop it up with the flash button in the auto mode. If it won't pop automatically in low light, then it certainly sounds defective.

You probably have "bracketing" turned on. In your menu settings, search for bracketing and make sure it is off.