There seems to be no need to worry. This originally concerned me too, but I\'ve rebuilt several times and re-registered when I\'ve reinstalled GS (160). The return email is generated almost immediately so you get your install code and just go right ahead. As far as I\'m aware there is no limit on the number of times you install, unless anyone knows different.
Still, it does seem strange; I can\'t see how that helps to prevent piracy for GS... not my problem, I guess!