#I am running minecraft from a folder via a batch file:

set APPDATA=%CD%\data
cd data\.minecraft\bin\
java -cp minecraft.jar net.minecraft.LauncherFrame

#Error report reads:

java.lang.ClassNotFoundException: net.minecraft.client.MinecraftApplet
	at java.net.URLClassLoader$1.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at net.minecraft.GameUpdater.createApplet(GameUpdater.java:423)
	at net.minecraft.Launcher$1.run(Launcer.java:87)