This article illustrates the logic according to which the Component Object Model (COM) determines which version of an Office application loaded when using Office Automation.

When a COM server is first installed or registered, and adds entries to the registry that match programmatic identifier (PROGID) and the class identifier (CLSID) of the server. These registry entries to enable COM to retrieve information related to a particular server, such as the location where the server is installed, to allow the user to automate this server. For example, Excel 2000 has the version-independent ProgID of Excel.Application and CLSID {00024500--C000-000000000046}. COM registry records for Excel 2000 are as follows: HKEY_CLASSES_ROOT \ Excel.Application \ CLSID
Default: {00024500--C000-000000000046}
\ LocalServer32 HKEY_CLASSES_ROOT \ CLSID \ {00024500--C000-000000000046} Default: C: \ PROGRA ~ 1 \ MICROS ~ 1 \ Office \ EXCEL.EXE / automation

When your computer has multiple versions of Office and using automation to one of the Office Server, version to be loaded is determined by these registry settings. In most cases, the rule is that the last installed version is the version that is loaded with the automation, however, presents a different behavior from other in Office Word applications. The following sections describe the different behaviors of each server automation of Office.

versions of Access, Excel, and PowerPoint 97, 2000, 2002, 2003 and 2007

Access, Excel, and PowerPoint, you can change these keys to the registry during the installation of Office. When you automate any of these applications, you load the latest version.

Word 97

Word 97 modifies these registry keys during the installation of Office. When you automate Word, if it is installed Word 2000 or Word 2002, Word 97 loads only if it is the latest version.

Word 2000, 2002, 2003 and 2007

Start Word 2000, 2002, 2003 AND 2007 change these keys to the registry during the installation of Office and every time. When you automate Word, the latest version is loaded initiated by the user or the latest version installed.

Additional Notes

A common perception for the automation of Office when you have multiple versions of Office installed on a system is that you can dictate the version is loaded using a version-dependent PROGID specific (for example, that "Excel.Application.9" Load Excel 2000, load the "Excel.Application.10" loads Excel 2002 and "Excel.Application.11" Office Excel 2003). This is not correct. Excel 2000 and later versions of Excel, you can share the same CLSID, so that the version that is loaded with these ProgID depends solely on which this was the last version.

For testing purposes, developers can force a specific version of an Office application to record using the / regserver command line. For example, to force a version to record without running the installer, you can use a command line similar to the following:

"C: \ program files \ microsoft office \ office \ excel.exe" / regserver

For more information about running multiple versions of Office or side-by-side installations of Office, click the following article in the Microsoft Knowledge Base article below:

Source: support.microsoft.com