In order to enter BIOS, you need to hold F2 or Del. If your keyboard isn't working, use a known good USB piece. (Note that some computers don't work SETUP with an USB keyboard. If your computer is old, and it has PS/2 ports, it may not support USB until after Del time).
If you see the blue "welcome" screen, then the system has loaded. That screen is there to keep you entertained while your user settings are loaded and your desktop is created, and if one of your drives is gone that could take a long time. Have you tried waiting it out? For, like, an hour.
In order, I'd try this:
a) Get/borrow a new keyboard and try F2 and Del as the system boots. Some BIOS settings trigger of the keys are tapped, others if held. Check to see if "Num Lock" toggles on your keyboard. If it does not, your USB hub is not working correctly, try a different port. Note mouse doesn't work by design in Welcome Screen.
b) Remove each drive in turn. Open the case and remove the data cable. One drive will boot, the other won't. Use the drive it boots and try to get into Windows. if it works, your second drive is likely on its way out.
c) Is the screen you are stuck on still animating? If it is, wait it out. All disk attempts time out and it will eventually start. Does Num Lock still work while on that screen? If the screen isn't animating and your Num isn't working, then if froze, in which case I'd start looking into a power or heat issue.
This is unlikely to be related to a power button force.