Battery or Camera causing the problem?

Wondering if anyone could help me.
I have a Nikon d40 dslr, I haven't used it in the last few days due to being busy with other things. I remember that I had just under half a battery left, I tried turning it on today and there's no light or anything.
I'm needing to get a new battery charger as mine is needing replacing as it isn't charging, I plugged my camera into my laptop tried turning it on again.nothing… I don't know why I even assumed plugging it into my laptop was going to do anything.
But usually when I barely have any battery left, it won't let me take pictures but let me view. So I'm not too sure if perhaps my camera is needing looking at or if it could possibly be my batteries?

You'll never charge a D40 from your computer.

Get a new charger and a battery. That way, if your existing battery's a dud you'll still be able to shoot, and if it's working, you'll have a spare.

You can't charge Nikon Li-ion batteries from a USB port.

If the battery charger shows a light when the battery is inserted, it is charging. Usually the light blinks while charging and stops blinking when fully charged.

If you have ever left your battery fully discharged for any length of time, this could be the reason for the battery not fully charging. While Li-on batteries can last a long, long time and can stay charged for months, if you fully drain it and leave it that way, the battery can suffer.

I have old Nikon Li-ion batteries that are about ten years old and they still can be charged and last a long time (over 700 shots per charge)

It sounds like just the battery is dead… Not a charger issue. You can get a new battery for your camera here… I got one for my canon and it works great:

http://www.batteries4less.com/contents/Static/camera-camcorder-batteries.html

If that's the original battery that came with your camera, it may need replacing too already. Pick up one at the same time you buy the charger.

Plugging your camera to the USB slot of a computer uses the camera's battery. Try to keep that in mind. That's why it's better to use a USB card reader. That would make three items in you shopping list the next time you go to the photo supply shop.