Will changing my operating system void my PC warranty ?
No, moving to another Operating System (for example Linux-based one or to Windows one, and vice-verca) will not void your warranty. Your warranty covers the hardware.
The only thing is that if you need to reach to HP support teams (official support teams) they might not be able to assist you with software related issues if you run an operating system which is not officially tested or supported. But your warranty will remain valid.