Do you have to reinstall windows if you change your CPU
also, when changing your motherboard do you have to delete the drivers like when you change your GPU
Windows does not have to be reinstalled if your CPU is changed, just make sure the CPU you want is compatible with your motherboard.
As for the motherboard, WIndows can be extremely fussy about whether or not the installation will boot from a motherboard swap; I've had motherboard swaps BSoD when trying to boot and other such quirks, so generally, if you are changing your motherboard, it's wise to wipe and reload a fresh copy of Windows so it doesn't have an identity crisis if it does manage to boot up. Would need re-activating anyway, too.
drivers should just reinstall automatically. If you're swapping out with the same chipset, there wont be an issue. If you are swapping in a newer chipset, you might run into some issues, but i think after a few reboots you should be fine.
The only REAL problems you'll encounter is when moving from an intel platform over to AMD or vice-versa. Only then should you have to reinstall windows.