>>1
You don't. Use Unicode, the global character set of which Shift_JIS is merely a subset. If you run Windows, your OS is internally Unicode, so all you need to do is install the Japanese IME (Input Method Editor) by adding it in keyboard languages (its location varied from Windows 2000 to Windows XP/2003, look around the Control Panel, regional configuration). This will enable you to type Japanese characters into Unicode applications such as Firefox or Notepad.