I have a Seagate (Legacy) 1 TB FreeAgent Go external hard drive. I had it connected to my laptop and when I moved it accidentally came unplugged (so it was not ejected properly). When i went to plug it back in, the lights on the unit blink (although not sure if they have always blinked because it's usually in a case) and the computer no longer recognizes it. I took it to my desktop and it was not recognized there either. I checked the drives (on both the laptop & dekstop) and could not locate any additional drives for the external H.D. like I used to.
Most of the data on the drive I can re-copy but there is a portion of it I would like to recover.
check the drive data port..see if you broke any of the pins or the connector. also check that the cable for the drive is fine on both ends. if the drive is out of warranty you can open the case and pull the hard drive out and connect it to one of the ide/sata ports on your mb or use a cable like this one. http://www.newegg.com/Product/Product.aspx?Item=N82E168...
the problem is if you dropped the drive and it had a crash...you may be able to use third party tools to recover the data if it a physical head crash then you may not without sending the drive to a data recovery lab. if the system is reading the drive i would look into drive recovery software to see if it can fix the error causing the drive not to be seen.