LyX
LyX is a free document processor that encourages an approach to writing based on the structure of your documents (WYSIWYM) and not simply their appearance (WYSIWYG). You can download it from lyx.org. You can combine it with a LaTeX package like MikTeX.
As described in this thread, for an existing MiKTeX installation is it recommend to disable the Automatic Package Installation of MikTeX. This is done through a temporary change in the registry entry.
<package
id='lyx'
name='LyX'
reboot='false'>
<variable name='REVISION' value='2.0.0'/>
<variable name='SUBREVISION' value='-3'/>
<variable name='MIKTEXREVISION' value='2.9'/>
<depends package-id='miktex'/>
<check type='uninstall' condition='exists' path='LyX %REVISION%%SUBREVISION%'/>
<install cmd='%COMSPEC% /c reg add "HKLM\SOFTWARE\MiKTeX.org\MiKTeX\%MIKTEXREVISION%\MPM" /v AutoInstall /t REG_SZ /d 0 /f'/>
<install cmd='%SOFTWARE%\LyX\LyX-%REVISION%%SUBREVISION%-Installer.exe /S'/>
<install cmd='%COMSPEC% /c reg add "HKLM\SOFTWARE\MiKTeX.org\MiKTeX\%MIKTEXREVISION%\MPM" /v AutoInstall /t REG_SZ /d 2 /f'/>
<remove cmd='"%PROGRAMFILES%\LyX20\Uninstall-LyX.exe" /S'/>
</package>