Is there a way in SQL Server Management Studio 2005 (or later) to change the Windows Authentication user (as you could in SQL Server 2000 and older)?
This is the gen
One other way that I discovered is to go to "Start" > "Control Panel" > "Stored Usernames and passwords" (Administrative Tools > Credential Manager in Windows 7) and add the domain account that you would use with the "runas" command.
Then, in SQL Management Studio 2005, just select the "Windows Authentication" and input the server you wanna connect to (even though the user that you can see greyed out is still the local user)... and it works!
Don't ask me why ! :)
Edit: Make sure to include ":1433" after the server name in Credential Manager or it may not connect due to not trusting the domain.