After turning off why doesn't it start back up

I have an older pc and I've been trying to find some answers. I had this Christmas decoration that plugged into a USB port so I had it plugged into my computer. Today I wanted to use my computer so I used my mouse to try to get the monitor on and it wouldn't come on. ( Stupid me it wasn't turned on) so I decided to shut the computer off and turn it back on. I did so but now all it does is peep a few times then the fan comes on and stays on and the screen remains black. It's done that before every time I turn it off by the power button. How can I get it back on

4 minutes ago by Philip Jessup