As pointed out by Lloyd, your path should use "Windows NT". In case of doubt, always use regedit
to go inspect the registry manually.
Edit: To go with your edit, you can simply GetValue
on the keys you find, the following code should do what you're looking for:
RegistryKey OurKey = Registry.LocalMachine;
OurKey = OurKey.OpenSubKey(@"SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList", true);
foreach (string Keyname in OurKey.GetSubKeyNames())
{
RegistryKey key = OurKey.OpenSubKey(Keyname);
MessageBox.Show(key.GetValue("KEY_NAME").ToString()); // Replace KEY_NAME with what you're looking for
}