Bought the same "omni" HD 120 Gb, same problem, resolve it today!
Here the solution.
1. Plug HD into USB port (does not matter which one)
2. Go control panel (enable classic view)
3. Administrative Tools
4.Computer management
5.Under storage (make sure it it - on the left), click on disk management, it will show the HD but it will say "unallocated" point the mouse on the black line, right click and select partion, the process will guide you through and at the end computer will recognise it as drive E:.
Hope it will help!
