(This was copied from GreyVulpine's instructions at: http://pastebin.com/1knuj6Zh )
    Download the minecraft.jar from minecraft's site, here:
    Download it to your desktop.
    Put it in a folder where you can access it easily.
    In the same folder, right click inside, choose new -> text document
    Double click to open up the text document in notepad, paste these two lines in:
    java -Xmx256M -Xms256M -cp minecraft.jar net.minecraft.LauncherFrame
    Go up to File -> Save as
    Change the file type to "all files" and save the file name to anything that ends with .bat,
    eg Run.bat.
    Run the .bat file by double clicking on it.