Registry access in Windows 7

I'm working on a program which uses RegOpenKey() and RegQueryValueEx() to access a particular registry key. Usually the key gets accessed like this:-

but I've just noticed that if I change it to this, it fails on Windows 7:-

Although it seems to still work in Win8.1 - so is registry access case-sensitive in Win7? I'm just curious because that'd be quite unusual for Windows. :confused: