What is the Registry
The registry is the master repository (all contained in a single file) of configuration information for Windows. It contains information about the system, files, users, and applications . Most applications will store information about themselves, or the user, in the registry (an example would be the high score in a game). There are many “tweaks”, “changes”, “enhancements” and occasionally even “fixes” that can only be done by changing a value in the registry. Many of the things on this page apply to all versions of Windows (NT, 2000, XP, 2003), but this page is focused on the MS Smartphone Operating System, Windows Mobile, which is based on Windows CE. A tool known as a registry editor is needed to view and/or update the registry.

When you look at the registry, it has a directory tree structure, similar to looking at directories with File Manager. There are four root trees in the registry, occasionally refered to as hives. Here are the four root trees, along with their abbreviations.

Name _______________Abbreviation ______________Usage
HKEY_CLASSES_ROOT______HKCR ________File association information (ex: how Windows knows what application to use for an MP3 file)
HKEY_CURRENT_USER______HKCU ________Configuration information about various things, supposedly related to the current user
HKEY_LOCAL_MACHINE_____HKLM ________Configuration information applicable to the device (or to all users)
HKEY_USERS______________HKU_________Not used on the Smartphone (Info on other users who are not logged in)

Note: HKCU can be a bit confusing because it has information about applications, the OS, and everything else, just like HKLM. It’s just that this information is supposed to be applicable to the user currently logged in, whereas HKLM is for all users. Since a Smartphone doesn’t ask you to login, you could make a pretty good argument that whether something goes into HKCU vs HKLM is somewhat arbitrary. Applications are free to use either HKLM or HKCU to store information, and some even use both.

“HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Splash Screen\CarrierBitmap” is an example of a registry key. In fact, this is the place where one of the bootup pictures is defined. Technically speaking, “CarrierBitmap”, is the value, and the rest (first part) of the string is the key. However, most people will call the entire string, the key. However, the registry editors tend to use the precise terminology. Comparing it to File Manager, you could think of the “Key” as the directory, and the “Value” as a file that contains one value. In the example I used in this paragraph, the data would be the pathname (on the phone) for the picture (JPG or GIF file).

One final note, there are a few different types of values that can be stored in a registry key: a String, a Group of Strings (MultiString), or a Number (called Double Word, or DWORD).

Registry Editors
Unlike Windows XP or 2000, the Smartphone does not come with a registry editor, so you will have to locate and install one (or more, I’ll explain why later). Fortunately, there are several free registry editors available, so it’s not really a big problem (although sometimes you get what you pay for). There are two types of registry editors that can be used (and I use both types). The first type is installed and runs entirely on the Smartphone itself. The second type installs on your PC and is run from the PC, but it uses Activesync to update the registry on the phone. The second type is easier to use, as long as you have a PC to connect to. If you are away from a PC with Activesync, then ones that run on the phone are the only option.

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