Nikon D90 Recording Problem?

When I would record video with my camera after 45 seconds of it recording video it would just stop recording, I looked at the settings in my camera and they are fine, the battery life is perfect and my camera is only 4 years old.

And your memory card is either not formatted in the camera or is too slow. Format the card in the camera and make sure it's a class 10 for SDHC or the fastest card available in the type you use.

It is the memory card problem for most dslr cameras you need a class 6 or higher card (class 10 is usually recommended) for recording videos all other cards are too slow to write video files onto the card

Did you follow the procedure found on page 50 of your manual? What did the icons say? That's where I would start. If necessary, you can download your manual from Nikon.

As for a class 10 card, I videoed with mine with a class 4 card. It didn't shut off, but it would skip while recording because the card was too slow. Since it is only HD, not full HD, a class 6 card is all you need.

It's not a camera problem, you are not using the proper memory card. Class 10 cards are cheap these days - buy one of those and your problems will go away.