At times, you may want to run SQL Server Management Studio as a different user than the AD account that you are logged into Windows. This command run from the command line will let you do just that (your path to the location of ssms.exe may be different). Change the domain\admin_user to the user you’d like to “run as”:
runas /noprofile /netonly /user:domain\admin_user “C:\Program Files (x86)\Microsoft SQL Server\100\Tools\Binn\VSShell\Common7\IDE\ssms.exe”
Note! If you are running this command locally, leave off the “/netonly” property – Thanks DCON!