A few thoughts...
Can you hear if the hard drive is spinning up? Maybe with the external USB HDD casing open, you could at least feel if it's vibrating slightly.
Is this USB enclose drawing all its power via a single USB port. Some external USB cases either provide a second USB connector for power, or give you a mains PSU. Describe the scenario for yours - it could be the unit is just not getting enough power...
You mentioned 'laptop'. Do you have a desktop machine? If yes, it might be worth opening the case of the desktop and seeing if you can attach the hard drive directly to one of the motherboard interfaces, IDE, SATA, what ever it is you have. Now look in Disk Management as per Vacunita's post...
ROGER - G0AOZ.