There isn't really such a concept as trial mode on Windows, since we aren't providing any system for selling games or collecting money on Windows. You are free to sell your game yourself if you want, but if you do that it is up to you to collect the money, track whether the game has been purchased, and implement whatever kind of trial mode makes sense for your business model.
We do support the same framework APIs on Windows as on Xbox, for testing purposes. The trial mode emulation works the same as it does in the Creators mode Xbox runtime. More details: http://blogs.msdn.com/shawnhar/archive/2008/09/17/trial-mode-in-xna-game-studio-3-0.aspx
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