It's in the "system" folder, which is hidden by default. In Windows, you can either change your folder preferences in Explorer to show hidden folders ("Organize" button in Vista>Folder and Search Options>View tab), or you can open the Kindle "drive" in Explorer, go up to the address bar, and simply add system\. For example, my Kindle is f:\. In Vista (and I guess Win7) it looks like you can't type in there but you can - just click in empty space in the Explorer address bar and it will change from "buttons" to a field you can type in. Screenshots attached.