Welcome to Swap Magic 3 Official Web Site no modding needed, well maybe some tools they give you.
as for the USB thing, you should really be using a USB stick, i dont know if it will see a hard drive, but a Stick should work
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http://www.generalemu.net/
Intel Core 2 Quad Q6600 @ 3.4Ghz (425x8), Leadtek GTX 280 1Gb, 1.8Tb HDs, 2Gb Corsair DDR2-800 @ DDR2-1020 5-5-5-18 Dual Channel
Dont PM me for help, use the forums, thats what its for!