Typically if hard drives are going bad you will hear them ticking not really squeeling. If its squeeling it could be a fan either in the power supply or on the cpu fan. If the CPU fans get clogged with dust it can cause your motherboard/processor to overheat and over long periods of time can fry the motherboard. I have had quite a few drives go bad on me and each on ticks like a clock.
At least you have a PC that works Jim
