This code is just do as in comments
//gets the local machine registry settings
RegistryKey rkStartUp = Registry.LocalMachine;
RegistryKey StartupPath;
//opens the registry key in which all the windows startup applications are configured
StartupPath = rkStartUp.OpenSubKey(@"Software\Microsoft\Windows\CurrentVersion\Run", true);
//checks if ABDXYZ application is in startup settings, if not exists as startup //app
if (StartupPath.GetValue("ABCDXYZ") == null)
{
//adds the startup app for ABCDXYZ, so that this application will start when windeos starts
//next time
StartupPath.SetValue("ABCDXYZ", Application.ExecutablePath, RegistryValueKind.ExpandString);
}