It seems there's some confusion here! I use Win 7 (like millions of others I guess) and have never succeeded in 'manually' adding FSG Alaska, Hawaii (nor the updates) to my scenery library. (Not sure about NA, or if it had to be added to the libarary in the same way).
The FSG download wrapper tells you straight up to add Alaska and Hawaii to the Library as scenery areas. It adds that in the case of Win 7 I "may need to click on the respective scenery folder and then right-click in the dialogue window to enable." It I'm sorry but I have been unable to understand/implement these instructions in a way that adds any scenery.
But wait - from what I am now reading in this thread it appears you don't actually need to add them as scenery areas. Which is right?
I have 'Addon Scenery' enabled in the Scenery Library. Does this mean FSX will automatically detect all the entries in that folder, including Alakas, Hawaii, NA etc? Whatever, some clarification needed I think.