I've installed 7-Zip in XP and it creates a context-menu in Windows Explorer. But, in Windows 7 it doesn't. I don't know why. I tried it with administrator privileges, but nothing happened.
It works fine on my installation.
Open 7-Zip and go to
Make sure that they are ticked. If it isn't perhaps file this as a bug report, but it certainly works here.
The problem is that Windows 7 uses different context menus for 32-bit and 64-bit applications.
I fixed this problem by installing the 64-bit v9.10 beta version of 7-Zip. I then opened it as an administrator. I was then able to set 7-Zip file associations and apply the context menu.