Maybe the enter key has a build up of debris, try using compressed air to clean the keyboard. If still unresponsive, the enter key is broken. You can use alternate methods such as control M, or replace keyboard.
If the screen is frozen it is most likely because the laptop is undergoing too many too many tasks at once. Try waiting a few minutes for it to finish current applications; then close and uninstall all unnecessary programs. Another problem could be that your laptop doesn't have enough RAM to handle that many applications at once. Try closing and uninstalling some software, then handle tasks fewer at a time.
This loud noise is most likey from the fan. It is probably dirty and covered with dust. Try taking a can of compressed air and blowing it through the vent. You can also try a mini vaccuum if need be. The fan also makes noise when overheated. If the noise still persists the fan is probably broken; you can find instructions to replace fan in the troubleshooting section.