ошибка A call to an OS function failed

function StopService(ServiceName: string) : string;
var
schService,schSCManager: DWORD;
ss: _SERVICE_STATUS;
begin
    schSCManager := OpenSCManager(nil, nil, SC_MANAGER_ALL_ACCESS);
    if not schSCManager = 0 then
    begin
        schService := OpenService(schSCManager, PChar(ServiceName),SERVICE_ALL_ACCESS);
        if not schService = 0 then
            if ControlService(schService, SERVICE_CONTROL_STOP, SS) then
                result:='OK'
            else
                result:='FAIL'
        else
            result:='Служба не найдена';
        CloseServiceHandle(schService);
    end
    else
    begin
        RaiseLastOSError; //<<<<<<<<<<<<<<<<<<<<<<<<<<<<<ERROR ЗДЕСЬ
        result:='(MANAGER)Ошибка';
    end;
    CloseServiceHandle(schSCManager);
end;

if not schSCManager = 0 then
if not schService = 0 then

if schSCManager<>0 then
if schService<>0 then

  if not (schSCManager = 0) then