However, if you look in your user folder, AppData (for me the full path is
C:\Users\Mark\AppData\Local\Temp\MediaPortal Installation\deploy
obviously your username will be different, and it may be different for other operating systems)
You will see two files
package-mediaportal.exe
package-tvengine.exe
these are the relevant parts of the installer. Run them in turn, and follow the (fairly obvious) instructions to run the update again.
AppData is a system folder, so you may have to make it visible using 'Folder and Search Option' (view tab).
Mark