download SeaTools from Seagate. Preferably the version you burn to a CD and boot from it (this way Windows doesn't get in the way).
If the BIOS doesn't detect it, most likely you're going to struggle. But SeaTools MIGHT find it and be able to run diagnostics. If it can't, double check that data and power cables are connected properly and try again.
If nothing else works, the drive might have gone completely.