There is a massive amount of operating systems already. List of operating systems.
Why would you like to create a new one? A lot of the existing systems are specialized for use case and or hardware.
If you want something for general PC use then you have the software problem afterwards, an OS is useless without software support. You need a critical mass of supported software before it takes off. Means money and time.
If you want to make it windows compatible you have the copyright problem, if you are flying to close to the sun it will burn you before you get to your destination .