Download Seagate's free diagnostic tool set, Seatools for DOS. I prefer the "for DOS" version. You use it to burn your own bootable CD-R (or floppy if you have one). Then you boot from that with absolutely no need for any working HDD. It loads a mini-DOS into RAM and lets you run all its diagnostics from a menu. Make sure you are working ONLY on the suspect Seagate unit.
Run the diagnostics and see what it says are its problems. If they are bad you may need to chuck the HDD and buy a new one. But if not, use its tool to Zero-Fill the disk. This also forces it to check every sector and replace any bad ones with good spare ones. It takes a long time, and it is possible if there are a lot of bad sectors that it could trip the SMART alarm for too many. But if it completes that, Windows will find it is dealing with a flawless HDD and should be able to handle it smoothly.