If your BIOS can see the drive, then you can test it. Go to the Seagate website and download their Disk Tools for DOS. You have to run the downloaded file to create a bootable floppy disk. You then boot from that floppy. It will load a simplified DOS and run some utilities that can test the HDD thoroughly and tell you if it has problems.
Of course, to do this you need another computer to access the website, and a floppy drive and cable to hook it up if you don't already have one installed.
One of the more common kinds of simple problems is poor connections where cables plug into sockets. The metal contacts can get oxidized or dirty over time. The simple thing to try is to CAREFULLY unplug the data and power cables at the HDD unit, then plug them back in again. Do this two or three times. Do the same with the data cable where it plugs into the mobo connector. This action MAY just scrape the contacts clean if that really is the problem.