Youtube Video: http://www.youtube.com/watch?v=9CjtJDAz1xo&eurl=http://www.fakku.net/
Download Link : http://www.fakku.net/viewtopic.php?t=6980
Totally discovered this by accident when looking for more stuff related to Tomoyo After, since I couldn't get enough of that gray-haired beauty. It's your typical move-through-the-stage-and-beat-everybody-up game, but involves your favorite characters from CLANNAD as well as some other interesting characters. Even Hard Gay, Nanoha, Suigintou (from Rozen Maiden), Hatsune Miku, and Ai Enma (from Jigoku Shoujo) make their appearance!
Once you start playing post some screenshots, I didn't really have time to post any good ones.
This game works perfectly on XP, but only if your regional settings have been set to Japanese. That being said there are two fixes if you cannot get the game to work on Windows:
Regional Settings
To set your computers regional settings to Japanese, go to the "Regional and Language Options" in the Control Panel and, under the "Advanced" tab, set the "Language for non-Unicode programs" to Japanese.
Microsoft AppLocale
If, however, you don't want to change the language setting, the alternative would be to use AppLocale, which you can download here. After installing it, run AppLocale, and run the game through Applocale in Japanese.