Applications typically use the Registry in one or two ways. The most common is to use it as a repository of application-specific information, such as user preferences. The type of information that the applications store depends on how the developers chose the keys to organize their applications' information. A second approach that application developers use with the Registry is to create an application that presents a user interface to the Registry entries that other programs can create and use. Several of the Control Panel applets work using this approach. These applications relieve you from having to edit the Registry manually to change system attributes.
If you are interested in seeing how the Registry stores the attributes of any given application, use regedit to start the Windows XP Registry Editor and go to the location HKEY_CURRENT_USER/Software to see the list of companies that have applications installed on your system. You'll also notice there are subkeys for each of the versions of products you have installed on your system. Be sure not to change any of these subkey values because it could cause the application to not work.
Given the two approaches software developers have for working with the Registry, there's no real surprise that the first one is most often defined upfront during the install process for many applications. The second approach is most often used for handling system-level utilities.
Moving an Application using regedit
As your systems fill up with applications, it's often necessary to move an application's location from one folder to another, or from one physical drive to another. One approach is to uninstall the application and then reinstall it in the new location. The trouble with this approach is that you lose all the preferences defined with the previous installation. It's back to square one to define the preferences you want in your applications. There's got to be a better way, and it's called working with the Registry.
Suppose that you need to move an application from C:/AppDir to E:/AppDir after installing a new E: drive in your system. The first step is to move all the data files over. Don't move the application files; Registry subkeys will handle that. Follow the series of steps shown here for moving the location of an application from one physical location to another:
Open the Windows XP Registry Editor from the command line by typing regedit from the Run command line.
Select Find from the Edit menu.
Type C:\AppDir, and press Enter. The Registry Editor searches for the Registry entry that contains C:\AppDir, and selects the first one it finds.
Press Enter to edit the value's data.
Type in the new folder name, which will be D\AppDir, as defined before, and press Enter.
Now press F3 to continue the search. You need to change every location in which C:\AppDir is shown to reflect D:\AppDir. After that task is completed, the application will be changed to this location.
You can go back to the Registry and check to make sure the change has been accepted.