This is dictation.Here are some quick suggestions that might be of some help to you. Is more likely that one of the fans inside your computer could start to make noise before the hard drive fails. Hard drive manufacturers a very conscious set up noises from their drives and they make every effort possible. Use the acoustic noise level of their hard drives. Cancer and much less costly to replace then the hard drive, so you should consider first the possibility of an only being a fan that is starting to wear. But even a fan that has worn bearings can still last a long time if you're willing to accept the noise level.
Another consideration is the buildup of dust bunnies. That term is used to refer to the accumulations of dust that sometimes can make noise or otherwise interfere with the cooling system in your computer. Dust is one of the things that contributes to the wear and tear on the fans. Your computer probably has three different fans. One on the CPU itself, another on the power supply and the third is for the entire chassis. You did say your computer was a desktop.
Now about the hard drive. You may have to open the case of your desktop and examine it while it is running. Of course, you need to be very careful about running the computer with the cover off. There is a danger dropping something into the computer and it would do a lot of damage. What you want to do is try to identify the source of the noise. I'm guessing it's going to be found with one of the fans and not the hard drive. However, if it really is the hard drive, then you need to make a backup of your entire system as soon as possible. A backup hard drive unit is only a fraction of the cost of what you paid for your computer when new. And having a backup can save you a loss of time trying to recover information that could be lost. In fact, hard drive for coverage is not as easy as you think it should be. In some cases a hard drive failure can be catastrophic with practically no warning.
Sorry if that sounds frightening, but from my own experience with hard drives I've learned that you have to have a backup plan. You must have a backup of your important personal material as well is having some way of restoring the operating system to its normal state.
So that is the best I can do for your at this moment. Bear in mind I have to do this with voice-recognition software, so you might see some very strange and on grammar expressions are words that the computer didn't understand. Just remember, computers are not perfect. Microphone off
End of dictation. 
