In case you don't know what is ReactOS, ReactOS is a free and open-source operating system based on Windows XP/Server 2003's functionality, while being able to run some NT 6 applications.
For more information about ReactOS, click here. You can also click here.
To download ReactOS, click here.
ReactOS's homepage: https://reactos.org/
ReactOS's forum: https://reactos.org/forum
Warning: ReactOS is in heavy development and it's in alpha stage currently, this means no guarantee for stability and safety. It's for evaluation and testing purposes only in this moment. If you want to use/test ReactOS, it's hlghly recommended to install it with virtualization software, such as VirtualBox or VMware. Informaton about setting up ReactOS is here, and a list of supported virtualization software. I tested ReactOS, and while the warning above is true, I am very satisfied with ReactOS generally. It is completely looking and working good.