What if I need to install windows 7? Is it possible?

installing windows is not for everybody

installing windows in bootcamp is more difficult

you can if you find it easier you can install it in a virtual machine such as virtualbox

otherwise you can try to get the help from somebody with more experience in installing windows

or you can read some of the many guides

https://manuals.info.apple.com/MANUALS/1000/MA1583/en_US/boot_camp_install-setup _10.7.pdf

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guide to install windows 7 bootcamp

or watch some of the many videos

https://www.youtube.com/watch?v=2S5YM-TQ-nc

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guide to install windows 7 bootcamp

As you probably have seen, new Macs no longer support Windows 7 through Boot Camp. This does not necessarily mean that your Mac cannot run Windows 7, but Apple has dropped official Windows 7 support for your Mac. In other words, you can run Windows 7 but it will not work as you expected. You can only install Windows 8, Windows 8.1 or Windows 10.

In case you want to install Windows 8 or a newer version through Boot Camp, open Boot Camp Assistant (in /Applications/Utilities) and follow its steps. If you need an installation guide, check the Boot Camp support website -> https://www.apple.com/support/bootcamp/

However, if you really need Windows 7, your only option is to install it in a virtual machine. A virtual machine can be used to run two operating systems at the same time, so you can use one or the another as you wish. Have a look at this tip to know more about virtual machines and its advantages and disadvantages -> Windows in BootCamp or Virtual Machine?

To run a virtual machine there are different apps you can use. If you are looking for a free app, VirtualBox is your choice, but there are paid apps with more features like VMware Fusion or Parallels for Mac. Finally, remember that you will get less performance on a virtual machine, so if you want to run games or heavy apps, you should install Windows 8 or Windows 10 through Boot Camp.