I know there must be so many questions just like this, but none of the solutions I tried did anything.
I've recently upgraded my RX 580 to a 5700 XT while running Windows 7 x64. After upgrading and the first time boot, I checked for any BIOS updates, there were none so I assumed everything was okay. When I logged into Windows 7, obviously the drivers wouldn't work and the display adapter would be "Standard VGA Graphics Adapter" (When no other drivers are available). After running the latest version of the drivers (19.7.2 I believe), everything installed normally, I allowed the display driver to install and rebooted. However, after we see the familiar "Starting Windows" animation with the logo coming together, as soon as the logo had been created, the system stays for about 20 seconds then powers off with no blue screen or message. I booted into safe mode to check the issue and the culprit had been the 5700 XT's drivers. After uninstalling, the system booted.
No matter what I try, I result in the same power off.
If anyone asks, I've tried these steps so far.
-Used DDU to wipe any traces of the driver and then reinstall.
-Reset the BIOS to default settings.
-Install only the display driver using the standard Windows update driver.