Well do you have any ideas on what the problem might be? Is it common? 
Also, it's not like it says how to install it on here anyway. Did I do it right? 
Archiving tool: 7-zip 
1: Open minecraft.jar and minecraftforge-client-3.3.7.135.zip 
2: Select everything in minecraftforge-client-3.3.7.135.zip and copy it over to minecraft.jar 
3: Delete META-INF 
  
EDIT: Okay stupid me. There is a readme file at the bottom of the zip file. But the installation instructions were the same as what I did! What's wrong?