If I am not mistaken, the maximum score in Vista is 5.9. They raised it to 7.9 in Windows 7.
Taking into account scales:
You: 77% of max (W7)
Your friend: 96% of max (Vista)
The scale is sort of arbitrary, it's just to give you an idea of performance in a simple manner. A more serious independent bench like those from PassMark will give you a more consistent picture of the actual performance difference.