Using custom directory does not work on beta 1.7.3

I was trying to use a custom directory for beta 1.7.3, to avoid it from corrupting my worlds and such, and when I was going to make a new world, I noticed that all my 1.6.2 worlds were there, indicating that the game was not using the directory I specified. I looked in the folder where my beta 1.7.3 files were meant to be, and I saw that there was nothing there. Also, the name of the folder was "Minecraft_Beta_1.7.3", and the path I specified was "C:\Users\Nick\AppData\Roaming\.minecraft\Minecraft_Beta_1.7.3"