You are specifying RegistryView.Registry64
so it will be retrieving the value from SOFTWARE\Microsoft\Windows NT\CurrentVersion
If you specify RegistryView.Registry32
it will retrieve it from SOFTWARE\WOW6432Node\Microsoft\Windows NT\CurrentVersion
instead (that is, on a 64-bit system; on a 32-bit system the WOW6432Node doesn't exist so it will just use the normal hive instead).
I think that if you specify RegistryView.Default
it will select the hive according to the bitness of the calling process.