On Win7 64 system which didn\'t have any editon of SQL Server installed, i installed Visual Studio 2012 for Web. I tought it will give me option to install SQL Server 2012 E
It should install with no problem, I just did this a couple of weeks ago exactly in the same order, first VS 2012 and then SQL Server, and it worked flawlessly.
Just install and setup SQL Server following the setup, reboot and you'll be able to connect from VS's DB Explorer.
If that doesn't work your best bet is to reinstall everything from scratch.