The Windows Vista DVD has a fixed keyboard layout. The Windows Vista DVD starts the Windows Preinstallation Environment (Windows PE). Windows PE may be configured to use only one keyboard layout. Therefore, when you use the Windows Vista DVD to start the computer, only one keyboard layout is available.
For example, the Japanese edition of the Windows Vista DVD uses the Japanese 106/109 keyboard layout. Therefore, if you have a Japanese 106/109 keyboard connected, the keyboard works as expected. However, if you have an English 101/104 keyboard connected when you use the Japanese edition of the Windows Vista DVD to start the computer, unexpected characters may appear as you type. When you use an English 101/104 keyboard together with the Japanese edition of the Windows Vista DVD, you cannot directly type a backslash (\) or an underscore (_).