Can I use a key to turn on my computer?

[nethmitharusha]

I visited to one of my friends home and he used a key to turn his computer on.the computer had a keyhole and he inserted the key and turned the key and the computer turned on.it was super.there is no button to press.if the key is not there no one can't turn on the Pc.How can I do this cool trick to my computer too?