Package preview-latex runs LaTeX on equations and other environments (figures and tables) of your source and replaces the fragment of the source by an preview image. In the “edit mode” for equations, you see the normal LaTeX code.
Homepage: http://www.gnu.org/software/auctex/preview-latex.html
By far the easiest way to get this combination going is by downloading the latest precompiled Emacs for NT including AUCTeX from http://www.gnu.org/software/auctex/download-for-windows.html and adhering to the installation instructions in the same place.
As an alternative a useful perl program known as latexmk.pl works well under cygwin, and provides a dvi “preview window” which updates on every page save. This gives a more stable “realtime” preview of your Latex document.
latexmk -pvc yourdoc.tex opens a preview window that continuously reflects changes to the tex source
LatexMk comes as standard with the popular tex installation MixTex? but is also available from ftp://ctan.tug.org/tex-archive/support/latexmk/ .You may have to make some changes to the perl file as detailed in the INSTALL file
You can incorporate some of the latexmk commands into the Auctex C-c C-c cycle / Toolbar menu using M-x customize-group auctex.
pdflatex "\nonstopmode\nofiles\PassOptionsToPackage{active,tightpage,auctex}{preview}\AtBeginDocument{\ifx\ifPreview\undefined\RequirePackage[displaymath,floats,graphics,textmath,sections,footnotes]{preview}[2004/11/05]\fi}" "\input" toto.texpdf2dsc toto.pdf toto.prv/tmp33492THG/preview.dsc