To run a program as another user, you can’t right click the program and choose “Run as…”
To run a program like the Microsoft SQL Server Mangement Studio 2008 with another user credentials:
start > run > cmd > runas /user:DevMoss200904\srvTest "C:\Program Files (x86)\Microsoft SQL Server\100\Tools\Binn\VSShell\Common7\IDE\Ssms.exe"
Enter the password for DevMoss200904\srvTest:
After entering the password the program should start with the given credentials, in this way you can test Windows Integrated security permissions on a database.