How to: Verify Whether Outlook Is a Click-to-Run Application on a Computer

Click-to-Run is a software delivery and updating mechanism available to Microsoft Office 2010. Products delivered via Click-to-Run execute in a virtual application environment on the local operating system. This means that they have private copies of their files and settings, and that any changes they make are captured in the virtual environment. Click-to-Run is fast—users can start running an application within a short time without waiting for the entire product to finish installing. Updates are carried out automatically in the background, without requiring a user to first remove an installation or install patches. Click-to-Run products are virtualized and do not conflict with other installed software.

However, because a product delivered by Click-to-Run has private copies of all its files and registration, an add-in developer cannot determine the product's existence the same way as a product that has been installed on a client computer’s hard drive. Starting with Microsoft Outlook 2010, add-in developers should should determine whether Outlook has been installed, and whether Outlook has been delivered as a Click-to-Run product.


Only 32-bit Office 2010 is supported in the Click-to-Run virtual application environment, even if the client computer runs a 64-bit operating system.

To check whether Outlook was delivered by Click-to-Run on a client computer:

  • Verify if the VirtualOutlook key exists in the following location in the Windows registry:

  • The VirtualOutlook key is a REG_SZ value that contains the culture tag of the installed product language, such as "en-us".