Running multiple versions of Minecraft

Since the server is not 1.4.2 yet i thought i would share with you how to downgrade and run multiple version of Minecraft.

There are 2 ways I know of:

1-Jar copying:

Steps:
-Download MC 1.3.2 ( http://tinyurl.com/8sje8w8 )
-Copy Minecraft.jar to your desktop
-Update MC
-Benefit

You will now have 2 minecraft.jar files one with version 1.3.2
and one with 1.4.2
Whichever one you wanna use copy into the .minecraft/bin folder
(remember to make a copy of the file you are overwriting

2- MagicLauncher

Steps:
-Download MagicLauncher (http://tinyurl.com/9raeyuq )
-Download MC 1.3.2 ( http://tinyurl.com/8sje8w8 )
-Rename minecraft.jar for instance minecraft132.jar
-Update MC
-Run MagicLauncher
-Enter username and password( dont have to be premium )
-Click on Setup
-Comfiguration -> New -> Name it -> Copy from nothing ( - ) -> Hit Select and choose your renamed minecraft.jar then click OK
-Benefit

Very nice tutorial indeed keep it up buddy.
P.S:If possible make a video for some people to use magic launcher.

Didn't know some might have such a problem. Just one thing to say, in order to reach the .minecraft :
In Windows xp: Start > Run > %appadata% a folder should open, there you can search and find the .minecraft file.
In windows vista, C:\Users\AppData\Roaming\.minecraft.
Windows 7 is same as xp.
After you reach that file. Switch .jar files, remember, smaller size means older version (:

I heard that downloading the bin from a website is illegal. I use MCNostalgia.
MCNostalgia The video explains everything and make sure to backup your saves too. It also allows you to go to other versions.
EDIT: I researched about it and most people say it's illegal.