Torrented Windows 8 and installed it over my Macbook's bootcamp's Win7 partition. I was updating the drivers and it crashed. Restarted and got the blue error screen. Anyway way to go back to Win7 without reformatting?

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2011 BMW X5 xDrive 35d Vermillion Red Metallic/Black Nevada Leather
Options: ZCW, ZPP, ZRC, ZTP, 300, 386, 496, 4AB, 6FL, Combox, LED Coronas. 04/11 Production