Ok, I'm even getting frustrated FOR you. I've been there, so I can relate. Here's what I did for my wife's GN, using a Win 7 laptop (and a USB connected to the side).
1st/2nd try - thought I'd have the drivers installed since I already rooted mine and a Galaxy Tab 10.1, so I tried to unlock right away. Got to the point of Fastboot recognizing the device, no luck, so decided to go back in and go through all of his steps in the program. Having tried shortcuts with no luck, I finally decided to go in and delete every single Samsung related driver there was (Wug has clues for what to look for in the software).
Final attempt - after clearing out all drivers, I went through and did the step by step check of configuring the drivers. During the process, there were a couple of times where I thought something was wrong (little yellow triangle in device manager), but I stayed the course with patience, and after a bunch of times with the device being re-recognized, I finally got to the final step of device configuration. You HAVE to be patient during downloads and devices being recognized. It take at least a few minutes. Yahoo!
Then went on to root according to Wug and all was fine. Moral of the story for me: don't assume anything is ok if you haven't gone back to square one and started, methodically, from the beginning. Perhaps you made a mistake or two like me?