Hardware backdoor is exist, but it only can perform low-level task (such as read privileged/private kernel memory).
I doubt those backdoor alone enough to steal your private and send it to the attacker without additional ttack vector such as physical access or software backdoor.

But this is highly theoretical attack and you don't need to worry about it unless your attack scenario is very serious.


Even if your PC comes with Windows OS (which most likely pirated because you didn't pay for it), all you need to do is format the drive and install with Linux distro of your choice.