If you can, just install iAtkos, use it to prepare your USB drive, then erase iAtkos' partition and install Snow Leopard with prepared USB drive on it.

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AMD Phenom II x4 810 2.6GHz | Gigabyte GA-MA790XT-UD4P | Gainward GeForce 9800GT 1GB | 6 GB 1333MHz DDR3 RAM | 1TB HDD | 19'' Widescreen Samsung LCD Display
Mac OS X Snow Leopard 10.6.4 (Everything works except Safe Sleep) | Windows 7 Home Premium x64