HDD External USB not recognized by Windows Vista. If Windows doesn't recognize your HDD external, check the following items in Control panel:

Double click Management tools > Computer management > Disk management. If the external hard drive, you must partition and format it to appear on your desk.

External USB hard drive not recognized by Windows Vista What to do?

To learn how to do the above, do this:

If the disc does not appear, try another USB cable and try disconnecting the disk. Then connect it again. Install the latest drivers from the motherboard, especially USB controllers. Visit your hard drive manufacturer's website for specific drivers and a page with frequently asked questions and answers.

If possible, check the node position (Sata1 / Sata2 for a sata disk) or make it master (IDE disk). Connect the hard drive directly to the motherboard cage to check if the defect comes from the cage or the hard drive.