using Microsoft.Win32;
...
/// Retrieve this value:
/// [HKEY_LOCAL_MACHINE\SOFTWARE\appname\myvalues]
/// "myvalue"="100"
/// </summary>
// Create a key that looks in HKEY_LOCAL_MACHINE
RegistryKey key = Registry.LocalMachine;
key = key.OpenSubKey(@"SOFTWARE\appname\myvalues");
key.GetValue("myvalue").ToString(); // Get value 100