My Windows Computer Won't Turn on, Why?

It sounds like you're talking about a desktop here. If the PSU worked before, it might still work now. But if it's not the original one, or it's from another machine, that's one thing. Interpret the "30 seconds" as meaning that you unplug everything, buy a new CMOS battery, which you'll replace before you remove the old one, or pull it out if you can't remove it, and with a metal object that conducts current, short-circuit it for thirty seconds, then insert the new battery or plug it back in, and everything else as it was. Plus, it's good to have a Windows 10 installation media USB plugged in. When the computer starts, it asks what to do, usually you have to press "F1" to go to the BIOS, where you can make a general setting or just set everything to default, which is not a very smart idea, because if it has a virus, it is better to set it up. and "First Boot On USB" where the OS is, then when it has been read and starts, you press the "DEL" button and "First Boot On Windows Start Manager" i.e. the Hard Drive and then throw everything on it out during the setting, so that only the completely empty disk remains. but then you have to set up each driver in Windows afterwards, if not then "Driver Booster free or pro" , it might help. It's good if the Windows 10 on the USB is Professional RTM and has a key, of course. https://www.simplysup.com/