Why should you use LyX for document preparation?
If you use LaTeX you already know the advantage of a structured document preparation language with automatic typesetting.
LaTeX however has some disadvantages over Word.
LyX addresses all of these disadvantages, providing a WYSIWYM (what you see is what you mean) editing environment. It is robust and safe, in the sense that lack of LyX features does not prevent full use of the TeX language.
If you have never used LaTeX then using LyX as a front-end gives you GUI access to 99% of the functionality of LaTeX.
If you use TeX or LaTeX then LyX makes maths entry much easier, and allows proof-reading of the whole document (including pictures) within the edit window. You are free to continue to use arbitrarily complex TeX in your source code - worst case it will be displayed in source form in the edit window. Existing LaTeX documents can be easily converted to LyX, and LyX export to LaTex is as readable as LaTeX written by hand.
There is a whole spectrum of other attempts to make TeX more WYSIWYG - for a good overview of the pros and cons of each (including LyX) see the Uk TeX FAQ.
Installing LyX on Windows XP & Windows 2000 systems.
Last updated: January, 2015
The latest version 1.5.4 comes with a very easy to use installer - see this page.