If you are going to write to HKEY_CURRENT_USER you won't need Administrative rights.
on the other hand, writing to HKEY_LOCAL_MACHINE requires Administrative rights.
be sure when you open the key for writing to call it like this
RegistryKey key = Registry.CurrentUser.OpenSubKey(@"Software\YourAppPath", true);
if that doesn't work for you, there is a trick to write to the end of the executable file itself, but that's another thing.
