Why does my hard disc suddenly start making such a din? It seems to happen MORE OFTEN when I am watching a film on Netflix but it can occur less frequently just about any time. Is it the fan that needs oiling or replacing ... or is it time for a new computer?
In which case you have an overheating problem and possibly a fan about to fail. If this is a laptop take it in for a service otherwise if it is a desktop take the cover off and use a cardboard tube from a paper towel to locate the source of the sound. If it is a failing fan they are relatively cheap and easy to replace yourself.
That's good news! It's a desktop and I am going to remove the cover today. If it is the fan, would it be naïve of me to think I can solve the problem with a squirt of CRC 5-56 or WD40?
The fans commonly fail in just the way you describe. You will not solve your problem with WD-40, and you may worsen it. If the fan that is failing is a case fan; that is, mounted to the outside wall of the case, then it is an easy and cheap fix. If it is your CPU fan, or one on your video card, then it becomes more difficult.
Probably because the odds are the problem is a failing bearing. Once that bearing goes no amount of WD40 is going to fix it. It might make the noise disappear for a short while but the bearing is still worn and overheating. Ultimately it will fail completely and then you can have bigger problems with the MB, RAM and CPU overheating. For the cost of a cheap replacement fan it is not worth taking that risk IMO.
There are also freeware programs to monitor the temperatures of the CPU and hard drive and in some case allow you to adjust the speed of the fans. Right now my netbook that I am using now have a cpu temperature of 22 C and a hard drive temperature of 27 C degrees.
I don't think that hard drives have a dedicated fan. Cases do, usually one in front and one in back. You say it happens when watching films on Netflix....... I would think that videos put stress on your graphics card. So it could just as well be your graphics card fan, or maybe the processor fan. Proc fans are replaceable, graphic card fans are not. Cards are affordable and fairly easy to replace. As an aside, I sometimes open my case and CAREFULLY vacuum it out with a soft bristled brush and a wedge tool attached to a cannister vacuum cleaner. Some desktops have a foam filter behind the front grill. So don't forget to clean/vacuum that off too. This will all help keep the components cool which will cut down on fan noise because they are activated by heat. The hotter it is, the faster they will spin to cool it down, and the more noise they will make. Also vacuum the built up dust off the fan blades as much as you can. Every little bit helps. Good luck.
It might had zero to do with the cooling fans as a hard drive itself could be going bad and making such noises. If there is a bad area or areas on the drive so that it need to try to read that area over and over it could be the source of the noise also.
That was why I suggested using the cardboard tube to determine the source of the sound. If the hard drive is failing then the tube would locate that noise rather than one of the fans. As @Injeun mentioned it might be the cooling fan on the display card. That too can be located in the same manner.
