Macbook 2015 is the latest Apple laptop that does away with windows 7 support. So if you want to run windows on Macbook 2015, you will have to go with the Windows 8 64 bit edition and if you are person that loves experimenting, you can go ahead and install Windows 10 64 bit version on it.
Of course, if you have a copy of windows 7 and do not want to upgrade to windows 8 or 10, you can install Parallels and install any version of windows. That way you can even install windows xp on it. So 2015 MacBook Air and MacBook Pro line-up will be the last generation of notebooks with Windows 7 support.
For those who are not familiar with Boot Camp, it is a way that allows the user to install Windows operating system along with Mac OS X that comes pre installed on a Mac laptop or desktop.
It is interesting to see how Apple removed support for the most popular windows till now, which is the windows 7. Many users are not very fond of the Metro user interface that is being used in the windows 8 which is why those people sticked with the windows 7 instead of upgrading to the latest version.
Macbook 2015 is a great 12 inch laptop but too bad it would not allow user to run windows 7.