i have a sea-gate st500dm002 hard disk with me which i bought 1 years back it was working fine utill one day....suddenly my system got hanged so i rebooted the system but as a result the bios hangs at startup and my hard drive is not being detected at bios
i used to have that problem with old ide drives. it was either a master slave thing on the drive or i would have to reset the bios. also keep this in mind every seagate drive i have ever owned died for various reason within a few years. so you may have a brick.
if you feel the drive is fine get a usb drive dock. i got one its awesome you can hot swap the drive and no need to worry about the bios. and if you get one that has esata then you wont lose any data speed. i picked mine up on ebay for less then $30