I know PS 4.0 is ancient. But we're using it anyway on some dev servers it is not my decision.
I'd like to know if there's an alternative for Rename-LocalUser which requires 5.1+ Even if it needs calling wmic, I'm unsure if how to use that kind of call, please give me some examples in one or the other way.
Thank you
Abraham Zinala has provided the right answer in his helpful comments on how to approach this on older PowerShell versions.
You can either use Get-WmiObject to query the local user, and then invoke the .Rename(..) method:
$myAccount = Get-WmiObject Win32_UserAccount -Filter "name='theAccountIWantToRename'"
$myAccount.Rename('myNewUserName')
Or, recommended use of Get-CimInstance and Invoke-CimMethod since WmiObject is no longer available in newer PowerShell versions:
$myAccount = Get-CimInstance Win32_UserAccount -Filter "name='theAccountIWantToRename'"
Invoke-CimMethod -InputObject $myAccount -MethodName Rename -Arguments @{ Name = 'myNewUserName' }