In this video I give a full tutorial on how to install Minecraft 1.7.3 mods on Windows. What you will need for the tutorial is ModLoader, 7-Zip or WinRAR and your mod of choice (in this case TooManyItems).
Download ModLoader: http://dl.dropbox.com/u/20629262/Latest/ModLoader.zip
Download 7-Zip: http://www.7-zip.org/download.html
Download WinRAR: http://www.rarlab.com/download.htm