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If all you want to do is restart an app without any configuration go to menu>settings>applications>manage applications and tap on the "all" tab. Find the app and tap on it. there you can clear the cache and delete the user data. This is usually enough to set it back to the beginning as if it were freshly installed. If you suspect the app is corrupt and you want to re-install it, still clear data and cache and then tap uninstall as well. Now, before you re-install the app, plug in your phone to a PC and mount as storage. You will be looking for a folder with the app name preceded by a dot (the dot makes it hidden to Android). You may also have to set the PC to display hidden files and folders to see it. Don't worry if you still can't find it, because they may not be one, but if there is, then delete it. Now you can re-install the app as if it had never been present on the phone.