Windows 7: Registry Permission Group or usernames question

So, I'm getting access denied when trying to modify values in my Enum hieraki.
Trying to grant permissions just results in "Access denied"...

I have only one user on my system and that is an administrator.

Anyways, when right-clicking a node and choosing "Persmisions" there are several Group or usernames listed that can be granted different permissions.

I'm just wondering, what are all these "Everyone", System", Administator", Creator/Owner" etc. What do they represent?

They're group names (except creator owner, which is a special kind of permission which represents the user or group that first creates something). Note that certain areas of the registry even the admin can't modify (by default). You might want to check into the advanced section of permissions to make sure you have ownership of the key location (and it's subkeys) before trying to modify permissions on them.