Noisy CPU Fan & DVD R/W tray doesn't open

I have the following two problems:

1) Whenever I start my computer, the CPU fan makes a lot of noise and the noise remains until the desktop appears completely. I thought that the problem was with the fan, so I replaced it recently with a new one. But the noise problem is still there, which means that the problem is with something else.

2) DVD R/W tray frequently fails to open whenever the eject button is pressed. I either have to hit the case a few times so hard that it might break someone's head or pull the tray by sticking my fingers on both of its sides.

Please advise me on that. Thanks!