So I recently installed a new harddrive into my macbook for more space. It was working fine but just recently (after a couple days since it was installed) it started acting really strange. When ever I would shut it down and restart it the computer would not restart. It would stay on the blue screen with the apple logo and the spining circle below it. I found out that when I put the mac osx start up cd 1 in the computer and shut it down and restart it again it will start up after a couple min of the blue screen. When it does start up it takes me right into mac osx and everything is fine, everything is still on computer and computer works great. So I guess what I am asking is why does this happen and what can I do to fix it?