¿Por qué están fallando todas mis instalaciones de Windows MSI?

Parece que no puedo instalar nada nuevo en mi PC ya que todo está fallando con errores.

Actualmente en Windows 10 con las últimas actualizaciones.

Como ejemplo, cuando intento actualizar iTunes:

También he generado un registro para la instalación, aquí está la parte cercana al valor de retorno 3.

Action 19:43:38: ExecuteAction. 
Action start 19:43:38: ExecuteAction.
MSI (c) (48:CC) [19:43:38:709]: PROPERTY CHANGE: Adding SECONDSEQUENCE property. Its value is '1'.
MSI (c) (48:CC) [19:43:38:710]: Grabbed execution mutex.
MSI (c) (48:CC) [19:43:38:710]: Incrementing counter to disable shutdown. Counter after increment: 0
MSI (c) (48:CC) [19:43:38:710]: Switching to server: EXISTINGINSTALLDIR="C:\Program Files\iTunes\" EXISTINGIPODINSTALLDIR="C:\Program Files\iPod\" AUTORUN="#1" PROGRAMMENUNAME="iTunes\" REGSRCH_MEDIA_DEFAULTS="0" PCAST_URL_HANDLER="URL:iTunes Podcast" ITUNES_LANGID="1033" INSTALLDIR="C:\Program Files\iTunes\" AMDS_SERVICES_INSTALLED="{2E4AF2A6-50EA-4260-9BA4-5E582D11879A}" IPODINSTALLDIR="C:\Program Files\iPod\" FIREFOXDEFAULTSFOLDER="C:\Program Files (x86)\Mozilla Firefox\defaults\pref\" INSTALLERCACHE="C:\ProgramData\Apple Computer\Installer Cache\iTunes 12.5.3.17\" INSTALLDIR32="C:\Program Files (x86)\iTunes\" MEDIA_DEFAULTS="0" SOURCELIST="C:\ProgramData\Apple Computer\Installer Cache\iTunes 12.5.3.17\\;" TARGETDIR="C:\" UPGRADEFOUND="{955524E7-79EB-4CA9-BA4D-FD2DF587651B}" ASUW_IS_INSTALLED="{56EC47AA-5813-4FF6-8E75-544026FBEA83}" CURRENTDIRECTORY="C:\WINDOWS\system32" CLIENTUILEVEL="0" CLIENTPROCESSID="5960" USERNAME="[email protected]" SOURCEDIR="C:\Users\DarkL\AppData\Local\Apple\Apple Software Update\" ACTION="INSTALL" EXECUTEACTION="INSTALL" BUSEROSVERSION="10" ROO
MSI (s) (A8:60) [19:43:38:716]: Running installation inside multi-package transaction C:\Users\DarkL\AppData\Local\Apple\Apple Software Update\iTunes6464.msi
MSI (s) (A8:60) [19:43:38:716]: Grabbed execution mutex.
MSI (s) (A8:1C) [19:43:38:718]: MainEngineThread is returning 1603
MSI (s) (A8:60) [19:43:38:719]: User policy value 'DisableRollback' is 0
MSI (s) (A8:60) [19:43:38:719]: Machine policy value 'DisableRollback' is 0
MSI (s) (A8:60) [19:43:38:719]: Incrementing counter to disable shutdown. Counter after increment: 0
MSI (s) (A8:60) [19:43:38:719]: Note: 1: 1402 2: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Installer\Rollback\Scripts 3: 2 
MSI (s) (A8:60) [19:43:38:720]: Note: 1: 1402 2: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Installer\Rollback\Scripts 3: 2 
MSI (s) (A8:60) [19:43:38:720]: Decrementing counter to disable shutdown. If counter >= 0, shutdown will be denied.  Counter after decrement: -1
MSI (c) (48:CC) [19:43:38:721]: Back from server. Return value: 1603
MSI (c) (48:CC) [19:43:38:721]: Decrementing counter to disable shutdown. If counter >= 0, shutdown will be denied.  Counter after decrement: -1
MSI (c) (48:CC) [19:43:38:722]: PROPERTY CHANGE: Deleting SECONDSEQUENCE property. Its current value is '1'.
Action ended 19:43:38: ExecuteAction. Return value 3.
MSI (c) (48:CC) [19:43:38:722]: Doing action: SetupCompleteError
Action 19:43:38: SetupCompleteError. 
Action start 19:43:38: SetupCompleteError.
DEBUG: Error 2836:  The control Back on the dialog SetupCompleteError can not take focus
The installer has encountered an unexpected error installing this package. This may indicate a problem with this package. The error code is 2836. The arguments are: SetupCompleteError, Back, 
Action 19:43:38: SetupCompleteError. Dialog created

He mirado a mi alrededor y he estado probando todo tipo de soluciones, cualquier ayuda sería muy apreciada.