以用户身份从windows服务运行进程失败,访问被拒绝?

System.ComponentModel.Win32Exception: Access is denied
at System.Diagnostics.Process.StartWithCreateProcess(ProcessStartInfo startInfo)
at System.Diagnostics.Process.Start()

引发此异常的代码是:

_process = new Process
     {
     StartInfo =
        {
            Arguments = "",
            CreateNoWindow = true,
            ErrorDialog = false,
            FileName = instanceDirectory + "program.exe",
            WorkingDirectory = instanceDirectory,
            UseShellExecute = false,


            UserName = GetUserNameForInstance(_id),
            Password = GetPasswordForInstance(_id),
            Domain = ""
        },
    EnableRaisingEvents = true
    };

_process.Exited += ProcessExited;
_process.Start();

同样,这仅在作为Windows服务运行时抛出。根据Windows中的“服务”面板,该服务正在本地系统下运行。