Why is my machine being so slow with clicking noise?

Hi

I currently have the above model. Its my girlfriends and I was hoping to find out a few issues with it.

Firstly, the model was bought in 2006 and currently has 19.12 gb of space left on the internal HD.

The machine is very very slow, even with one or two programmes open.

She has adobe CS5 on the machine at the moment but it seems like the computer cant cope, although I have a similar model with the same software and there are no problems.

As well as the speed issue there is ;

-a lot of heat emitting from the left hand side of the machine

-a clicking/whirring sound coming through the left speaker.

-dvd player is tempramental

-speakers do not work

Is the processor not fast enough to handle the programmes?

Could there be an internal problem with one of the fans causing the heat and also the slow operating time?

Im at a bit of a loss so any help in getting this (otherwise perfect) machine up to speed would be amazing.

thanks in advance

David