[1.6.4][Windows 7][Warning: Noob Question!] Can't run Minecraft through Eclipse

I installed the Forge source according to the instructions on the Wiki and tried to run MC through Eclipse, but it spits out the following error log:

Aug 24, 2014 7:50:42 PM net.minecraft.launchwrapper.LogWrapper log

INFO: Loading tweak class name cpw.mods.fml.common.launcher.FMLTweaker

Aug 24, 2014 7:50:42 PM net.minecraft.launchwrapper.LogWrapper log

SEVERE: Unable to launch

java.lang.ClassNotFoundException: cpw.mods.fml.common.launcher.FMLTweaker

at java.net.URLClassLoader$1.run(Unknown Source)

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 sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)

at java.lang.ClassLoader.loadClass(Unknown Source)

at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:102)

at java.lang.ClassLoader.loadClass(Unknown Source)

at java.lang.ClassLoader.loadClass(Unknown Source)

at java.lang.Class.forName0(Native Method)

at java.lang.Class.forName(Unknown Source)

at net.minecraft.launchwrapper.Launch.launch(Launch.java:94)

at net.minecraft.launchwrapper.Launch.main(Launch.java:27)

Here's a screenshot:

http://i.imgur.com/LkF22VE.png

I know this is about an obselete version, and I'm probably showing my ignorance with this question, so I understand if you can't help.