If you still have warranty (a 1.5 TB drive can't be so very old), it will be free.
But you didn't tell what program in Vista didn't recognize it. The only reliable one in a case like this is Disk Management. Not (My) Computer or Windows Explorer or the BIOS. So, with a lot of luck, Disk Management will see it and let you repartition and reformat it. But I don't expect so.
Kees
Hello,
I have the Seagate Free Agent Desk P/N 9ZC2A8-500, 1.5TB external harddrive. Recently it starting beeping and the computer (Windows Vista o/s) would not recognize it. I unplugged it, removed the usb wire and replugged, same thing. Beeping sound from HD with no recognition. I unplugged again, shut down computer, removed computer power source, plugged computer power source back in after minute and when started up, plugged HD power source in and beeping started again.
Any words of wisdom would be greatly appreciated! Thanks.
Rich

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic