Minecraft Crash

---- Minecraft Crash Report ----
// Why is it breaking :(

Time: 18/09/13 16:49
Description: FML will not run in demo mode

java.lang.RuntimeException
    at cpw.mods.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:159)
    at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:471)
    at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:806)
    at net.minecraft.client.main.Main.main(SourceFile:101)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at net.minecraft.launchwrapper.Launch.launch(Launch.java:57)
    at net.minecraft.launchwrapper.Launch.main(Launch.java:18)


A detailed walkthrough of the error, its code path and all known details is as follows:
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-- System Details --
Details:
    Minecraft Version: 1.6.2
    Operating System: Windows 7 (amd64) version 6.1
    Java Version: 1.7.0_21, Oracle Corporation
    Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
    Memory: 161794600 bytes (154 MB) / 286523392 bytes (273 MB) up to 954466304 bytes (910 MB)
    JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
    AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
    Suspicious classes: FML and Forge are installed
    IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
    FML: