I believe it's not any of the choices you gave. Windows will probably object to changing that much of your hardware, but you will be in Windows when it does so and asks for you to get authorization from Microsoft. I've done that a few times, and it's a fairly quick phone call.

A few thoughts in no particular order:

I don't think the BIOS settings would do that if your new hardware is the right type (for example, not using a PCI card when the new motherboard wants PCIe, or a CPU of the wrong socket type), but I agree, that would be something to try: clear the BIOS. Problem is, the new motherboard is the source of the new BIOS settings and should allow you access to the new hardware.

Does it beep when booting? Does the motherboard have a 2-character alphanumeric code it displays? Knowing the motherboard maker and the codes can help a lot. For example, three beeps usually means to check memory etc. On mine, A0 is the correct boot code displayed.

Is it possible you did not connect the second power supply cable to the motherboard? Common mistake.

Is it possible you have too much power draw for your old power supply? To test that, unplug all disk drives, DVD drives etc. except your boot drive.

Could one or more of the new components be defective? Do you have other parts to switch in one at a time for diagnosis?

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