Sounds like your disk may be toast.
Do you know the make and model ? If not, open your PC to find out. Then go to the makers web site and download the diagnostic tools for that disk. Normally, all hard disk makers have such tools available publicly.
That tool will be able to tell you if your disk is good for the trash or not.
If it is not the disk, it could be the cable, or the motherboard. As for the cable, if you never move your PC I don't know how it could suddenly break down, so that would leave the motherboard.
Pascal.