I do not use a password to sign on to my computer nor does anyone else using this computer; therefore, we all have the same desktop. It is my understanding that if we used passwords the desktops would be different.
Sorry but your conclusion in this statement is erroneous. I'm afraid you've been misinformed. Having a password for each log in has nothing to do with how each user's login (desktop) is individualized. Passwords only restrict access to each user's account by other users.
To avoid confusion, think of these terms as synonymous: user's log-in, profile, account.
Each users desktop might be the same on your PC but that has nothing to do with lack of a password. And probably if you look closely, there are some differences on yours as well.
Each time you creat a user on your PC you create a profile--you don't mention which Operating System you use but I'll use XP as an example. In Window Explorer, these profiles are contained in the C:\Documents and Settings directory. All user preferences, including the appearance of the Desktop, which programs start when Windows starts, etc., are contained in each user's account folder in Documents and Settings. So, for example, the Desktop wallpaper can be different for--
C:\Documents and Settings\User1\
C:\Documents and Settings\User2\
So can you see how this relates to HKEY_CURRENT_USER? Hope this answers your question somewhat.