If you need to make a test connection to a MS SQL DB as a different Windows user, and you’re not using SQL authentication, you can do the following:
runas /user:domain\sqluser "C:\Program Files\Microsoft SQL Server\100\Tools\Binn\VSShell\Common7\IDE\Ssms.exe"
You’ll then see the following messages after being prompted for a password for that user:
Attempting to start C:\Program Files\Microsoft SQL Server\100\Tools\Binn\VSShell\Common7\IDE\Ssms.exe as user "domain\sqluser" ...