Paul Johnson has a great wiki article on how to get R and Emacs up and running. It is located here. I basically followed his advise to set up my Windows 7 system.
Paul's instructions take into account a lot of explanations and additional options. This page is to simplify it even further. I am going to show in just a couple simple steps how to set up just R and Emacs on Windows 7 64 bit.
1. Download and install this: http://pj.freefaculty.org/software/WinProgs/R-3.0.1-win.exe
2. Download and install this: http://pj.freefaculty.org/software/WinProgs/emacs-24.3-modified-2.exe
3. Download the zip file attached to this page below called R-Emacs_Scripts.zip
There are 2 files in the zip file. One is the framepop.el script and the other is the 50emacs-ess-ku.el startup script. Both of these are exactly like the ones on Paul's site except I have them in a single zip file for your convenience. When I tried to download them it was a pain because my browser kept opening them to view and then when I saved them there was extra html in the files that messed things up.
Per Paul's instructions put the framepop.el in the emacs/site-lisp folder and put the 50emacs-ess-ku.el script in the emacs/site-lisp/site-start.d folder.
That should be it. If everything installed correctly you should be ready to R with Emacs!