Help with fastboot please

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http://forum.xda-developers.com – My Infinity is unlocked and rooted. I want to install NVFLASH on my Infinity before I flash JB. The instructions for NVFLASH states you have to access the fastboot menu. When I boot and hold the volume down key I get to the boot menu. Then I press volume down to choose the fastboot icon and volume up to start fastboot. At this point the screen shows "Starting Fastboot USB download Protocol" and the same 3 icons are still on the screen. That's as far as it goes. I'm not sure if I'm actually in fastboot. Is this the fastboot menu or is something else supposed to happen? I don't know if (HowTos)