Cant read external hdd

Hi , I have just change my PC and my Imation Apollo 2.5 Portable HDD 250GB is not recognized when i plug it in. It only shows unknown device when i go into the device manager.

My motherboard is Gigabyte P61A-D3 currently running on Windows XP SP3

Other external HDD works fine on my PC expect for Imation Apollo. My Imation Apollo definately is not faulty as it can run on other computers, laptops EXCEPT on my new PC! I'm also using it with the correct USB cord as I'm using the same cord to try it on other PC and laptops and it works.

I have tried the following:

1) uninstalling the driver, scan for hardware changes, still the same.

2) Tried changing my OS to windows 7, still the same, read as unknown device.

3) Went to Disk Management, the HDD is not shown there.

4) I have tried plugging my Imation Apollo into every differnt USB port, USB 2 port show it as unknow device, USB 3 ports totoally no response as though i never plug anything in. (All my USB ports, whether USB 2 or USB 3 are working fine as I've tried other devices and external HDD)

5) I have tried going to Bios and disabled my USB 3, still shows unknown device

6) I have tried updating my motherboard with the lastest Bios from GIgabyte server, still shows unknow device.

7) I have tried installing Mass Storage Device Driver from third party, still shows unknown device.

8) I have also tried installing USB 2 drivers, still shows unknown device.

9) I have tried shutting down the PC, plugged off the power supply and waited more than an hour and try, still shows unknown device.

Can any kind experts help me on this? PLEASE! I'm desperate!