external wd hdd 1021 problem , windows 7

Hello, i bought a wd hdd 1TB which i first used it with Snow Leopard but there seems to be a problem when i try to use it in Windows 7 . The hard dirk is recognized as an external device and can be removed safely but no letter has been assigned to it since i do not see it in mycomputer. In the disk management there are 3 partitions for this external disk:
200MB simple layout, empty file system, good condition
931,19 GB simple layout, empty file system, good condition
128MB unlocated
I do not know what to do. Does anyone have any suggestions?
Thank you in advance.