How to make a USB PC Locker

foreach (System.IO.DriveInfo drive in System.IO.DriveInfo.GetDrives())
{
	if ((drive.DriveType == System.IO.DriveType.Removable))
	{
	}
}

[DllImport("user32.dll", SetLastError = true)]
static extern bool LockWorkStation();

bool result = LockWorkStation();

if (result == false)
{
	throw new Win32Exception(Marshal.GetLastWin32Error());
}

foreach (System.IO.DriveInfo drive in System.IO.DriveInfo.GetDrives())
{
	if ((drive.DriveType == System.IO.DriveType.Removable))
	{
		label1.Text = label1.Text + " " + drive.Name;
		string resumeFile = drive.Name + @"locker\locker.txt";

		if (File.Exists(resumeFile))
		{
			System.IO.StreamReader myFile = new System.IO.StreamReader(resumeFile);
			myString = myString + " "+myFile.ReadToEnd();
			myFile.Close();

		}
	}
}

if (myString.Contains("91999"))
{
    // do nothing
}
else
{
	// lock computer
}