What is the Registry?
The registry has two basic concepts to be aware of: Keys and Values. Registry Keys are objects that are basically folders, and in the interface even look exactly like folders. Values are a bit like the files in the folders, and they contain the actual settings.
When you open the Registry Editor for the first time, you’ll see a treeview on the left-hand pane that contains all of the keys, with values on the right-hand side. It’s about as simple as an interface gets.
The root-level keys that you see in the left-hand side of the screenshot are important. Each one houses a different set of information, so depending on what you are trying to do, you’ll need to know which section to browse down into.
Windows uses this section to manage file type associations, and it is usually abbreviated HKCR when being referenced in documentation. This key is actually just a link to HKLMSoftwareClasses.
You can also use this section if you want to tweak the context menu for a particular file type.
Holds the user settings for the currently logged in user, and is usually abbreviated HKCU This is actually just a link to HKEY_USERS
All of the system-wide settings are stored here, and it is usually abbreviated as HKLM. You’ll mostly use the HKLMSoftware key to check machine-wide settings.
Stores all of the settings for all users on the system. You’ll typically use HKCU instead, but if you need to check settings for another user on your computer, you can use this one.
Stores all of the information about the current hardware configuration. This one isn’t used very often, and it just a link to HKLMSYSTEMCurrentControlSetHardware ProfilesCurrent.