I've been trying to make the SQLServer FDO work with Windows Authentication,
but no luck yet.
I've tryied to create a connection from MapGuide Studio after connecting to
the server using both the MapGuide Credentials options and the specific user
Also tryied to prepend the domain name to the user (DOMAIN\UserName) but it
did not work.
In the SQLServer there were matching logins defined and connection on the
tested users was successfull when connected through the SQLCMD tool.
The only way I've found was to fallback to mixed mode authentication and
create a SQLServer security managed account.
The same happened while trying to use the FDOUserManager, which did not work
until I used a SQLServer account.
Are you connecting to SQLServer for spatial data or are you using the ODBC provider to get attribute data?
I don't believe it will be possible to use Windows Authentication using the Spatial provider because there is no DSN or connection string the user can modify.
Even in the case of ODBC where the user can specifiy to use a Trusted connection or Integrated Security the mgserver.exe service would probably have to run under a network id with privileges against SQLServer for this to work.
I don't believe the current model supports this option.