[xplorer˛] — The Registry part I: Introduction
home » blog » 11 May 2008

xplorer˛ stores its settings in the registry, but what on earth is this registry? In the old days (before windows 95) programs saved their settings in a plain text file called WIN.INI, which over time grew to be huge and messy, so the registry was born as its replacement. The idea is largely the same: a file somewhere on your hard disk that keeps program settings (e.g. where was the xplorer˛ window on the screen last time you used it) and system settings — your hardware configuration for example.

You will read many myths about the registry, like it is this sacred place that mere mortals should not enter without risking doom. Rubbish! True, you can damage your system if you start modifying or deleting entries in the registry willy-nilly, but mere "read-only" inspection is safe and indeed liberating experience the first time round. So let's try it: Click Start then pick Run menu command and type regedit and click OK. That's it, the mighty registry.

As you see after running regedit, the registry looks like a virtual hierarchical filesystem with a familiar tree/view user interface. You have registry keys ("folders") on the left, with subkeys, and if you click on one you see its content on the right hand side pane. These "files" (values is their registry terminology) have a descriptive name and contain some data. All too familiar, isn't it? All these "folders" and "files" even have context menus, right click on them and see what happens — but do not try any command that modifies anything, remember we are in read-only mode!

If you start browsing the contents, you will realize that there's a huge amount of information in the registry, but it is well organized in thematic groups. There are four main categories called hives which appear as root folders in the tree view:

  • HKEY_CLASSES_ROOT: HKCR Contains mostly information for windows shell. Under here you will find all the filename extensions that define the document types on your computer. For example HKCR\.jpg defines JPEG images and lists actions that appear in windows explorer (and xplorer˛) when you right-click on a JPG file, e.g. which program is associated with image files.
  • HKEY_CURRENT_USER: HKCU is where all your personal settings are stored for all the programs you use. For example xplorer˛ stores your bookmarks etc under HKCU\Software\ZabaraKatranemia Plc\xplorer2_UC. See the backslashes in this registry "path"? Just like paths separating real folder names, isn't it?
  • HKEY_LOCAL_MACHINE: Within HKLM you will find settings that are shared among all users on a computer. Details like hardware configuration or programs that start automatically whenever you boot your PC (see HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run). This registry hive is the most dangerous, so tread carefully making sure you see but do not touch anything!
  • HKEY_USERS: You are not the only user on the PC, under this key you'll find settings used by your wife and kids. HKEY_CURRENT_USER actually maps into one of the user ids under this key for the user currently logged on.

Technically speaking the registry database is spread among a number of files. There is a main part with information that applies for all users and particular files with favorite settings for each individual user. My settings are stored under C:\Documents and Settings\nikos\NTUSER.DAT.

So there you have it, the windows registry basics demystified. I hope your computer still works <g> Next time we'll see how to get some more useful information playing with the registry. The standard disclaimer follows for the litigious types in the audience :)


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