Putting an operating system on a computer your own doesn’t violate the EULA.
Depends. You may not legally use the same copy of Windows XP on two different machines.
In many cases, you can load it on a computer that replaces your old one, as long as you bought a retail version.
They no longer allow you to transfer an OEM version of XP to be loaded onto a new machine. They are bound to the motherboard. If a machine loaded with the OEM version of XP dies because of a faulty mainboard, it must be replaced with the same motherboard.
It does if the original copy was an OEM copy that came preinstalled on the old machine. Those aren’t supposed to be moved to other machines.