If you get no joy using the Troubleshooting Guide then try this...
You will need to check You Tube to find a Dismantle on your product and follow the step guide on here, the procedure should be similar.
Check 1st that your External HDD has an P.C. internal HDD inside, from You Tube, before dismantle of your External HDD.
Connections for an Internal Laptop HDD may have same connections as P.C. not sure though.Once your happy that it has continue reading and follow the step guide on the link below.
My neighbour has the Seagate FreeAgent Desk 500GB, and in under 2 weeks it started to beep and was not reconized by any Laptop or P.C. if this is the same for you with any FreeAgent Desk series ( not GO series, different procedure for GO products). You maybe in luck click this link, you may have to register in the forums to view thread....
http://www.yo-lid.co.uk/forum/viewtopic.php?f=32&t=84 Thread can be found in 'Technical' under 'General Technical Issues'
Thumbs up please if it's any use to you Thank you.