I switched to using a Dvorak keyboard part time around January of this year.  I now use a Dvorak keyboard full time and the last remaining issue I have is the logon screen.  Even though the keyboard for my user is Dvorak, the default Windows keyboard is still the standard English keyboard.  This means that I have to remember how to type my password 2 different ways; one for normal activities and the other for when I do a fresh logon to the computers at my desk. 

The easiest way to change the keyboard layout for logon is to modify the following registry key.

   HKEY_USERS\.Default\Keyboard Layout\Preload

Whatever the named value "1" is set to will be the keyboard layout present when you login.  By default on my computer this is the standard English keyboard (#00000409).  By setting this value to Dvorak (#00010409), the dvorak keyboard will now be used when do a fresh login.  You can find the keyboard layout code you are using by looking under the HKEY_CURRENT_USER\Keyboard Layout\Preload and Substitutes keys. 

Beware though, this will modify the keyboard layout for all fresh logins.  That means that anybody who TS's into your box will also be using this layout.  Not a good thing unless they all use Dvorak as well