system
A chat on subreddit /r/pcmasterrace
human
In addition to using sticky tape to stop them from being on top of it. Consider giving them a cat-tree or perch nearby that's higher up. Cat's like to be high up on a perch, and this one probably likes hanging out with you while you play on the PC. Give them an acceptable location to do this.

Edit: yes I already understood they like the heat as well. Thank you all for commenting that... However when given proper training and  acceptable alternative spaces they won't go near it; I've never had a cat go on my desk or PC cases or even keyboards.
gpt
Yes. My cat used to love curling up on my desk right next to the computer.  Now I'm in a new apartment and his cat tree is not far from my desk, guess who has a new favorite hangout spot!