Spilled a large amount of coffee over HP desktop keyboard. Immediately the monitor went black, computer wouldn't turn off. Have I killed my desktop? I've turned keyboard upside down over towels, but really worried that I've destroyed my desktop. I don't mind replacing a keyboard but is my desktop destroyed?
I write assuming no water got ON or IN the actual desktop computer chassis and that your keyboard is on one of the system's USB bus ports.
You have not killed your desktop. Just replace the keyboard.
What likely happened is that the keyboard shorted out due to the spill. The USB port saw excessive resistance and the motherboard shut down to avoid the possibility that sending excess voltage to the port would damage the port or other motherboard elements. Just disconnect the keyboard.
To encourage your motherboard to exit the panicked condition and discharge any odd power levels in various capacitors and circuits on the motherboard, disconnect the desktop chassis from its electrical outlet for 5 minutes or more.
Once 5 minutes or more have passed, connect the new keyboard to the system and power it up. You should be fine.