Here’s a quote from MajorNelson.com:
Download the XNA Creators Club Game Launcher (Xbox 360 HDD Required) in order to play the special preview selection of game demos created by the community using XNA Game Studio. When your download is complete, go to the Games Library, select My Games, and navigate to the XNA Creators Club category along the top. From there, press Y to view, download, and play the available trial games for this limited period.
The launcher is not available in Australia, Hong Kong, India, Korea, Mexico, New Zealand, Singapore, Taiwan.
On a sidenote, if you live in one of those countries that can’t download the XNA Creators Launcher, you can make an US account. This will also let you download demos, trailers, themes & gamerpictures that is only available in USA.