In PowerShell 3.0, the (hidden) object property PSTypeNames shows you the complete inheritance tree for WMI objects:
PS> $os = Get-WmiObject -Class Win32_OperatingSystem PS> $os.pstypenames System.Management.ManagementObject#root\cimv2\Win32_OperatingSystem System.Management.ManagementObject#root\cimv2\CIM_OperatingSystem System.Management.ManagementObject#root\cimv2\CIM_LogicalElement System.Management.ManagementObject#root\cimv2\CIM_ManagedSystemElement System.Management.ManagementObject#Win32_OperatingSystem System.Management.ManagementObject#CIM_OperatingSystem System.Management.ManagementObject#CIM_LogicalElement System.Management.ManagementObject#CIM_ManagedSystemElement System.Management.ManagementObject System.Management.ManagementBaseObject System.ComponentModel.Component System.MarshalByRefObject System.Object
As you can see, the instance of Win32_OperatingSystem is derived from CIM_LogicalElement, and you can use this WMI class instead to widen your query and get back all logical elements:
PS> Get-WmiObject -Class CIM_LogicalElement | Select-Object -Property Caption, __Class
In PowerShell 2.0, the property PSTypeNames does not include WMI inheritance information yet.
