What is the Registry?
he Registry is where Windows keeps the settings used to run Windows and all the installed programs. It can be as simple as where you chose a photo to use across the screen on Windows, the Registry remembers and opens it every time. To advanced security and configuration items.
When you install a program, many items are added to the Registry in the process and as Windows finishes the installation it removes most items not for regular use. Likewise, if you uninstall a program thru Windows process Windows removes the entries for that program in the Registry which can be numerous.
The Registry is stored in several files on the computer that are called hives. Think of them like hives that bees live in. The bees keep all their stuff in the hive (honey being one we most think of),
and the Registry has all the entries for the programs
The Registry has five hives when Windows is running and only three when Windows is shutdown,
One hive keeps the settings for the current user.
Remember someone else may log in your machine also and you may each have stuff set differently. This hive disappears when Windows is off. However, there is a hive for users, which includes all users and the current user hive is created from.
There is also a hive just for machine settings. There is also one called classes root that keeps up with where all settings are.
Now a warning about the Registry: If the Registry becomes damaged it may make Windows not work at all.
That is why when you see things mention a registry hack to fix something, it is always includes the warning to only do if you know what you are doing. If you go to change settings and make any type of typo you are at risk of losing everything on that machine. If you are not a person with an advanced knowledge of Windows, do not go in and do changes in the registry. Generally, when these worse-case scenarios occur, there is no fix without new install of Windows. There are several programs to allow editing the Registry, but to keep people out of trouble I am not listing, and yes, I know Google knows everything.
Hopefully you have a little more knowledge of Windows and how it works.