I usually do this to get volume information:

            ' Use WMI namespace WMI in which management options will be done
            If cUsername.Length > 0 Then
                loManagementScope = New ManagementScope("\\" + lcIP + "\root\cimv2", loConnectionOptions)
            Else
                loManagementScope = New ManagementScope("\\" + lcIP + "\root\cimv2")
            End If

            lcSQL = "SELECT * from Win32_LogicalDisk WHERE DriveType=3 AND VolumeName=""" + lcVolumeName + """"

            ' The ObjectQuery class represents a management query which returns instances or classes 
            loObjectQuery = New ObjectQuery(lcSQL)

            ' The ManagementObjectSearcher class allows the extration of an object management collection
            ' in regards to the query specified during the instantiation by the use of the
            ' ObjectQuery parameter or directly by a string
            loManagementObjectSearcher = New ManagementObjectSearcher(loManagementScope, loObjectQuery)

            ' The ManagementObjectCollection represents various object management collections extracted from WMI
            loManagementObjectCollection = loManagementObjectSearcher.Get()

But, on a domain resource, this does not work. I have for sure to pass the domain. So, I thought the username used would need to be replaced with Domain\Username. But, this gives a "The RPC server is unavailable." message.

Anyone has succeeded to use this across a domain?