Windows: how to remap right ALT to left ALT

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Keyboard Layout]
"Scancode Map"=hex:00,00,00,00,00,00,00,00,02,00,00,00,38,00,38,e0,00,00,00,00

Switch layout by pressing Caps Lock: http://playground.teerapap.net/2008/03/switch-input-language-by-caps-lock.html