External HDD

Help I have a 350Gb Freecom external HDD and I want to use it on my MacBook Air.

Unfortunately it won't recognise 80% of the time. I wonder whether the power of the MacBook Air isn't powerful enough to spin up the disks or have I got a faulty notebook.

Suggestions please

So you are connecting this external HD to the USB port? If the HD has an external power supply, use that and see if it works better..

No external power supply just connected through USB. It sometimes gets recognised so I don't get it!

Does the HD spin/power up every time? Do you have other computers on which you can try this? Has this always worked like this or is this a recent development? Are you running on battery on your MBA when you plug this device in or are plugged into power on the MBA?