Nikon D90 trouble in movie mode?

When filming i get light and dark bands across the screen but also filming at night there's loads of noise, the quality is really bad. I've tried different setting but i just don't get the HD what am i doing wrong? Desperate!

Well your first mistake is believing that film is the same as video… It's not. You can shoot film and you can record video but you can't do both at the same time. Perhaps a little boning up on your terms would help.

I'd suggest a call to Nikon. How old is the camera? What's the shutter count? They'll ask questions like that. You may have to send it to them if repair is required. Or worst case, the camera is just shot depending on its age.

When you shoot video in low light conditions, the ISO will probably be fairly high if you're using ISO Auto mode and depending on how you have ISO Auto mode set up. This is expected. High ISO gives good light sensitivity, but also increases electrical noise. To reduce the noise you can have more light on your subject and/or use a lens with a wide aperture like f/2.8 or f/1.8. Learn to adjust your camera's ISO manually. The D90 will do pretty good shooting at ISO 1600, much better at 800.

The dark band across the screen, I'm guessing you have some sort of fluorescent or sodium lighting illuminating your subject. These lights flash on and off at a 120 hertz rate which will cause a dark band which moves vertically. Use incandescent lights.