hell if your in london I can do it for you - for a small fee of course! and yes i do have the qualifications and several years of experience
having been building PC's for my local neighborhood for the last 2 years, and maintaining them and such. i have dealt with many many old PC's from 3- 12 years old. and there is nothing i like better than to clean out and sort out a good old PC
love the old buggers!!!
I will say however, there is no harm in you opening the side of the case yourself and taking a soft brush to the dust inside it and giving it a clean - and if the PC is 9 years old i imagine it will be a solid metal case so i doubt there will be any problems putting it back on.
with those cases there are normally two screws on the back of the PC that will release the side of the case and should be fairly easy to spot. if your looking at the back of the case then the screws will be down the right had side.
Once released, you can slide it backwards and then it will just lift out from there.
clean out the visible dust on everything with a soft bush. - then have a good look inside of the case.
commonly i find that The "Scream" is i would suggest dust build up in the fans on the CPU and the motor on the fan crying in pain as it cannot move, i say this with a little confidence.
It may well be any other fans on the pc that you are hearing to be "normal" and are still working ( for example a fan mounted on the rear of the pc. )
on older motherboards you will find that if the cpu fan won't spin the bios won't even respond or load up at all. you will never see a POST screen or manufacturers Logo. and old motherboards will suggest to the PC to shut down and leave the fans running to cool the pc down. in this case there will then be no signal sent to the monitor and the monitor will go into "standby" mode.