I have a TC-E17 Lens and a Nikon 8700. I do I connect them together. I have a UR-E17 lens adapter. How do I put this on the camera.

First, make sure that you have the right adapter to couple this lens to your Nikon. A universal adapter may actually fit and properly click into place but the electrical contacts may not match your Nikon. Make sure the electrical contacts on the adapter match the contacts on the camera body.

If they don't match, get an adapter specifically for Nikon and perhaps, specifically for your camera.

Once you have verified that it is a Nikon adapter, you need to make sure the electrical contacts between the adapter and the camera body are clean. Many people clean the contacts by holding the lens release button down and twisting the lens or in this case, the adapter, on and off ten or more times.

If neither of these options work you may need to contact Opteka, Nikon or both.

That depends on the lens. Sigma makes their lenses with a variety of mounts. If the lens has a Nikon mount then you don't need an adapter at all.

Since the Nikon lens mount has a deeper flange depth than other mounts, you cannot fit a lens with another mount onto a Nikon body without losing the ability to focus to infinity. Because of this, you won't find an adapter for another mount. Adapters are available to fit Nikon lenses onto other cameras but not the other way around.

please be more specific. what camera and lens

You can't dismantle the lens without causing permanent harm. You need to contact the repairer and tell them about this problem.

try these:-

• connect it to pc and on it
• vaccum the barrel of lens
• changing mem. card and batt. for 2min.
• shake it.
• on and off in different positions
• hit the part near lens softly with palm (trust me this made mine work)

77MM

This is probably THE most common failure among digital cameras. There's a halfway chance of fixing it yourself, described here: http://camerarepair.blogspot.com/2007/12/fixing-lens-error-on-digital-camera.html

You may have a dirty contact on the tc cpu pins. Try cleaning the pins with a clean pencil eraser or some methanol. You could also have a loose connection between the tc and the lens or body. Try applying a rotational force in both directions...see if you notice any change in behavior. If you have a local shop, see if you can try another copy on your lens.
The 17e may have slow-ish performance in low light, but it should still be usable. If neither of these issues is apparent then it may need to be exchanged or serviced.

The D40 will only autofocus with the Nikkor AF-S lens...look for the AF-S in the lens title. For 3rd party lens, only SIGMA with the USM title will autofocus.

To use the T-adaptor...you will need to use the "Manual" mode of the camera.

Take batteries out. leave overnight. make sure batteries are fresh or charged. Put 'em in did it work? No then Nikon Tech help in the first instance also take a look here http://www.fixya.com/support/p422-nikon_coolpix_8800_digital_camera/solutions