INFO: Registry Entries Made by an ActiveX Component

An ActiveX component can be either an in-process or out-of-process (local or remote) server. When registering an ActiveX component on a Windows 95, Windows 98, Windows Me, Windows NT 4.0 or Windows 2000 machine, specific entries are made in the Windows Registry that allow the components to be accessed by client applications. An ActiveX control is an example of an in-process server that is registered in the Windows Registry. The purpose of this article is to outline some of the Registry entries for an ActiveX component in order to assist in troubleshooting registry issues that may arise.

An in-process component can be registered by using a utility such as Regsvr32.exe. The utility makes a call to the component's DllRegisterServer method. At this point, a series of entries is made in the Windows Registry. The method for registering out-of-process servers can vary.

The scope of this article will only refer to one branch of the Registry: HKEY_CLASSES_ROOT. This same information can also be found in HKEY_LOCAL_MACHINE/Software/Classes. For troubleshooting and removal purposes, you only need to focus on HKEY_CLASSES_ROOT.

In the HKEY_CLASSES_ROOT branch, you will initially find a list of file extensions. Following the file extensions are a combination of Programmatic Identifiers (ProgIDs) along with special keys that will be discussed shortly.

ProgIDs are typically friendly names that refer directly to a component's ClassID. The typical format for a ProgID is <Application>.<Class>.<Version>. However, this format is not strictly enforced and often times the version portion is ignored. Examples of ProgIDs are "Word.Application.8" and "Excel.Chart."

Each ProgID refers to a ClassID. The ClassID (or CLSID)is formatted as {xxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxx}.

Along with ProgIDs, special keys such as AppID, CLSID, Component Categories, Interface, Licenses, and TypeLib are found directly below HKEY_CLASSES_ROOT. Information regarding your ActiveX component can be entered in any of these special keys. The focus of this article is only on the CLSID, TypeLib, and Interface special keys. For more information concerning these and other special keys, refer to the resources listed in the REFERENCES section of this article.

IMPORTANT: This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. For information about how to restore the registry, refer to the Help files in the Registry Editor (Regedit.exe).

You can use this information to remove all references of a given component from the registry or to troubleshoot a possible registry problem.

The following steps illustrate how you can step through the registry and find references to an ActiveX component:

1. Run the Registry Editor (Regedit.exe).
2. The first step is to find the Programmatic Identifier (ProgID). This can be found directly under the HKEY_CLASSES_ROOT branch. Again the typical format is <Application>.<Class>.<Version>. For example: MSComDlg.CommonDialog.1.
3. Once you have found the ProgID for a given component, expand it and select the CLSID subkey.
4. In the right pane, you will see the ClassID that this ProgID is associated with. For example: {F9043C85-F6F2-101A-A3C9-08002B2F49FB}
5. Copy this ClassID by double-clicking the Default string icon and copying the value from the Dialog window that appears.
6. Select and expand the subkey HKEY_CLASSES_ROOT\CLSID. Note that the subkeys are ClassIDs.
7. Click the Edit menu and choose Find. Paste the ClassID value that you copied from the ProgID. Click the Find Next button to locate the value under HKEY_CLASSES_ROOT\CLSID.
8. Once you find the subkey, expand it. Note that there are several subkeys, including InprocServer32, ProgID, TypeLib, and Version.
9. Select the TypeLib subkey and copy this TypeLibID by double-clicking the Default string icon in the right pane and copying the value from the Dialog window that appears.
10. Select and expand the subkey HKEY_CLASSES_ROOT\TypeLib.
11. Click Find on the Edit menu. Paste the TypeLibID value that you copied from the ClassID and then click Find Next. The registry subkey that is found contains information about your component's Type Library.
12. Select and expand the subkey HKEY_CLASSES_ROOT\Interface.
13. Click Find on the Edit menu. Paste the TypeLibID value that you copied from the ClassID and then click Find Next.
14. Unlike the other searches you have completed, the search under the Interfaces subkey results in a one-to-many relationship between the TypeLibID and the InterfaceIDs associated with that TypeLibID. To find all the InterfaceIDs, click Find Next from the Edit Menu or press the F3 key.

"Inside COM" by Dale Rogerson, Microsoft Press (ISBN 1-57231-349-8)

For a list of additional resources regarding the Windows 95, Windows 98, or Windows NT registry, please see the following article in the Microsoft Knowledge Base: