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:domainsqluser "C:Program FilesMicrosoft SQL Server100ToolsBinnVSShellCommon7IDESsms.exe"

You’ll then see the following messages after being prompted for a password for that user:

Attempting to start C:Program FilesMicrosoft SQL Server100ToolsBinnVSShellCommon7IDESsms.exe as user "domainsqluser" ...