When investigating an issue with your Microsoft Office applications, you may need to determine whether you have the Windows Installer (MSI) based version of Office or the Click-to-Run (C2R) version of Office. These versions are based on different installation methods.
The MSI based version of Office uses Windows Installer technology, which is a traditional method of installing and updating Office. If you install Office by using MSI, you have to wait until the whole Office product is installed before you can open and start to use the product. The C2R based version of Office uses Click-to-Run, which is a Microsoft streaming and virtualization technology that allows you to open and start to use the product before the whole product is installed. Click-to-Run is the technology used to install Office 365 subscription products, while the MSI is used mainly to install the volume license editions of Office.
To find out whether your installation is MSI or C2R, in the Microsoft Office application, such as Word or Excel, go to File > Account. If you see an Office Updates section, the installation is C2R:
If there is no Office Updates section, then it is an MSI installation: