Usb external Hard Disk incorrectly powered

I have a Philip usb external hard disk ( the inside hard disk is Seagate barracuda 7200.11 750 gb) I accidentally connected the power cord going to the power jack in the wrong way and I smelt something inside burnt - when i tried to powered it again the correct way, it normally give the blue power-on light but the computer recognizes it as a "usb device and asking for the software - I know this is unusual 'coz before the computer will automatically recognize it as an external drive and assign a drive letter. Anybody knows if this HD can still be repaired or at least recovered the data. Please Help. thank you for any reply.

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