Close all instances of minecraft before doing the following:
- Download the 1.4.7 minecraft.jar: http://assets.minecraft.net/1_4_7/minecraft.jar
- Click on your start menu, in the search bar type %appdata% and hit enter. You should be in a Roaming folder
- Find the folder called .minecraft and open that.
- Find the folder called bin and open that.
- You should see a file called minecraft.jar or minecraft. Rename them to something else, for example minecraftold.jar
- Copy and paste that file you downloaded (Step 1) to that bin folder.
- Run minecraft.