Instructions on the highest and cheapest way to replace a bad hard drive on a Dingle Inspiron 8600 ?

Hard drives actually do go bad, its a fancy piece of machinery with very tight tolerances on the physical design, so they do just go hopeless.

Dell tech support is actually pretty good, they walked me through a similar problem on a different device. If you have a warranty, they will send a new disk within a time unit or two.

They shall tell you to try the diagnostics CD that came with your dell, or make you burn a new one. Provided this can't fix the disk, and you don't have a warranty, BUY A NEW DISK. The end is near.

Good Luck!