I know Ive installed forge right, It worked fine in 1.6.4, but now in 1.7.2 I get this crash log and Minecraft dosen't start up 

 

[13:35:44] [main/INFO] [LaunchWrapper]: Loading tweak class name cpw.mods.fml.common.launcher.FMLTweaker

[13:35:44] [main/INFO] [LaunchWrapper]: Using primary tweak class name cpw.mods.fml.common.launcher.FMLTweaker

[13:35:44] [main/INFO] [LaunchWrapper]: Calling tweak class cpw.mods.fml.common.launcher.FMLTweaker

[13:35:44] [main/INFO] [FML]: Forge Mod Loader version 7.2.211.1121 for Minecraft 1.7.2 loading

[13:35:44] [main/INFO] [FML]: Java is Java HotSpot Client VM, version 1.8.0_25, running on Windows 7:x86:6.1, installed at C:\Program Files\Minecraft\runtime\jre-x32\1.8.0_25

[13:35:44] [main/INFO] [LaunchWrapper]: Loading tweak class name cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker

[13:35:44] [main/INFO] [LaunchWrapper]: Loading tweak class name cpw.mods.fml.common.launcher.FMLDeobfTweaker

[13:35:44] [main/INFO] [LaunchWrapper]: Calling tweak class cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker

[13:35:44] [main/ERROR] [LaunchWrapper]: Unable to launch

java.util.ConcurrentModificationException

at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901) ~[?:1.8.0_25]

at java.util.ArrayList$Itr.remove(ArrayList.java:865) ~[?:1.8.0_25]

at net.minecraft.launchwrapper.Launch.launch(Launch.java:117) [launchwrapper-1.9.jar:?]

at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.9.jar:?]

Java HotSpot Client VM warning: Using incremental CMS is deprecated and will likely be removed in a future release

 

The bad thing is my computer is so shit, It can't run anything above 1.7.2. My graphics card is to out of date  :'(

ok, thank you for your help!