I have found a way to get the 1.7.2 version folder back. This will allow you to mod Minecraft 1.7.2. If this has already been found, then I am sorry about this and I will feel stupid. Here are the steps to mod 1.7.2!
1: Run Minecraft 1.7.2
There should already be a profile created for it
2: Generate a world
3: Exit MC
4: Go to %appdata%>Roaming>Minecraft>Versions>1.7.2
6: Cry when you open Minecraft the next time and see your modded folder erased and replaced with a fresh one. To install mods after 1.6, you actually need to do a little more than that.
5: Make a copy of the 1.7.2 folder and name it something else (In this example we'll call it "1.7.2 - Mods", but you can call it whatever you want. Use the chosen name instead, anywhere that I use "1.7.2 - Mods".)
6: In the copied folder, rename 1.7.2.jar to 1.7.2 - Mods.jar
7: Rename 1.7.2.json to 1.7.2 - Mods.json
8: With a text editor, edit "1.7.2 - Mods.json" and change the line "id": "1.7.2", to "id": "1.7.2 - Mods",
9: ...now you can start modding the "1.7.2 - Mods.jar" file.