What OS are you running? I assume you already installed the drivers. If not, than you will need to install the drivers for the enclosure box (eSATA/USB) in order to work. Otherwise windows doesn't know what type of device it is. Make sure that the driver(s) support your operating system. Double check all the cables & connections inside the enclosure box. Sometimes window doesn't detect certain type of plug-n-play device(s) or was disable in the BIOS. Reboot the system with the external drive power "ON" connecting to the system.
If all the above fail than do this:
1) Remove the drive from the enclosure box and connect the drive directly to your motherboard SATA controller.
2) Reboot the system and go into the BIOS and check to see if the drive is working. If the BIOS see it, than you know its not the drive but the enclosure bridge that cause the problem or other driver issue with windows.
3) Other thing you might want to try and narrow down the problem is, put in a different drive (a working drive) into the enclosure box and see if it works. NOTE: Assuming that the drivers that came with your enclosure box is compatible with your OS.
NOTE: The majority of enclosure box (eSATA, USB, 1394a/b) is not as friendly as they advertised. Trust me, I've seen this type problems everyday. The problem is drive compatibility. They don't test the enclosure box (bridge) with every brands of drive out there. 95% of the time its not the drive but the enclosure bridge (circuit board) itself. I highly recommend buy from a brand name only or if not buy the whole complete external drive unit.
Good luck!
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