According to Kieran Snyder, Program Manager on the Windows Globalization Team,

"... we have 130+ languages enabled in Windows Vista, impacting hundreds of millions of people. However, by giving customers the tools that we are going to be providing for free when Vista releases (Microsoft Keyboard Layout Creator and Microsoft Locale Builder), we are going to make Windows linguistically accessible for >90% of the world’s literate population – that’s over 3.5 billion people."

This means no more hunting for the €, © or ô symbols via Insert | Symbol in Word -- you can now assign any symbol to any key of your choice. Or, you can use a standard locale as a starting point to build a customized locale of your own, be it for Esperanto, Klingon, or your own private cipher for a civilization of one.

While the Keyboard Layout Creator already works with Windows 2000, XP or Server 2003 and will be supported in Windows Vista, Locale Builder is a tool specific to Windows Vista versions from Beta 2 forward. Put the two together on Windows Vista and you're all set to share your custom locale with anyone you choose (say, by creating a Worldwide English keyboard layout that uses a 24-hour clock and the lunar calendar).