About the Error
When running Setup to install Microsoft Office programs, this error occurs because Microsoft Windows Installer can only run one installation at a time, unless it is a nested installation.
Windows code 1618 - Read what really helps
The fix is simple: wait until the software which is currently installing finishes the process. Restart the computer if necessary, then install the next program.
TipFor more information, please see: How to fix Update error #1618