Cuzin,
You must do as mentioned above - change the directory CMD is working out of. For example:
CMD starts at, lets say,
Code:
C:\WINDOWS\System32
And lets say you unzipped the folder with nbimg to your desktop. You would type the address to that folder after "CD". This is what it looked like for me:
EDIT: Fail. I edited out my last name, but I forgot to edit the other part that shows it. Oh well. Don't stalk me please!