Script I used as computer statup script pushed via GPO. It renames local Administrator to Admin and sets password for Admin account to one specified in script.

Script was tested and used on Windows XP Professional.

' -------------------------------------------------------------------------
' Change local Administrator account to Admin and resets password
' -------------------------------------------------------------------------
On Error Resume next

Set objWMIService = GetObject("winmgmts:{impersonationLevel=impersonate}!\\.\root\cimv2")
Set colAccount = objWMIService.ExecQuery ("Select * from Win32_UserAccount where SIDType = 1 AND Domain = """ & strComputer & """" )

For Each rAccount In colAccount
  iLastSepPos = InStrRev (rAccount.SID, "-")
  strSID = Mid (rAccount.SID,iLastSepPos+1,5)

  If strSID = "500" Then
    Set objThisComp = GetObject( "WinNT://" & strComputer & ",computer" )
    Set oLocalAdmin = objThisComp.GetObject("user",rAccount.Name)
    oLocalAdmin.SetPassword ("Password123")
    oLocalAdmin.SetInfo

    If lcase(rAccount.Name)<> "admin" Then
      objThisComp.MoveHere oLocalAdmin.AdsPath, "Admin"
    End If

    oLocalAdmin.SetInfo
  End If

Next