Is it possible to boot into Windows at all? I would check Windows Event Viewer log for details.
It can be any of hardware components.
First, try to disconnect and then carefully install again graphic card and memory modules (Ground yourself before doing that!).
Check and wiggle all cables to verify that they are seated.
Verify visually that CPU fan spins.
Verify that CPU fan sensor is not faulty by looking in BIOS (when you can get there), the sensor RPM will show there.
If nothing helps, it's either graphic card, PSU or mobo. Having spare graphic card and PSU helps testing this.