Hey A1A2 - HD whine is not neccesarily an indicator that your HD is failing (or going to fail anytime soon). Some models are more prone to develop the noise than others. In addition, if it is in a "hot spot" inside your case, consistent heat can bring that whine on. Over the years, I have had Seagates, Quantums, IBM's, and WD's that start getting noisy. All of those drives are still running today. Some are 7+ years old.
However, if you are going to replace the drive you might want to consider relocating the drive inside the case. Most ATX cases are pretty restrictive, especially if you have two IDE HDD. Hard drives CAN get very hot.
What kind of case do you have? Do you have a front case fan? If so, it is really easy to drop a drive down in front (or near) the fan to help pick off that heat (i.e don't have to add any MORE noisy fans).