Authorization dbo maps to a user with an old machine name

I am trying to run a command that looks like this: Create ASSEMBLY [AssemblyName] AUTHORIZATION [dbo] From ... When this runs, it returns an error message: Could not obtain information about Windows NT group/user 'oldMachineName\username', error code 0x534. In this case oldMachineName is the old machine name for my computer. I changed the computer's machine name to newMachineName before every installing Sql Server, but there are obviously some vestiges of it hanging around. When I log into Sql Server using SSMS, it correctly lists the logged-in user as newMachineName\username. Yet when running this command with Authorization dbo it is trying to use oldMachineName. So, how can I convince Sql Server that oldMachineName doesn't exist anymore and teach it the correct group/user of the current dbo (ie: my logged in user)?