Macbook wont boot up help!

My macbook wont boot up for some reason. When trying to turn it on it goes to a grey screen and nothing pops up, eventually a little picture pops up that has what looks like a folder with a question mark in the middle. I then tried booting from the CD and when trying to do that a picture of the world pops up and then also the folder with the question mark in the middle. I thought i may have been the harddrive so i bought a new one and it still has the same problem.

If anyone knows what may be the issue please help out! Thanks alot

 

Yeah i tried booting off the CD drive, and instead of the question mark blinking it came up with a white screen with the mouse showing, and i tried resetting my PRAM too and that doesn't work either