.... ugh.. I hate to say this because I despise the software (I work in the Math dept), but LaTeX is your best bet.. it does all you need
It will run under windows and an awesome editor for LaTeX is WinEdt (
www.winedt.com).... WinEdt isn't too hard to setup, but sometime TeX is a bear...
LaTeX is free, WinEdt is about $30 but has a trial period of a month before anything happens...
I would also recommend Ghostscript and GSview which allow viewing of .ps files..
with the combination of these four programs you can create DVI, PDF, and Postscript files as well as view them..
but, beware the learning curve for this would be pretty steep, but you can pretty much do everything.. It is worth it if you are doing this for any length of time, but if it is only for a semester or so of math equations, try to find something a bit easier.