Weird Buzzing Sound When Playing Game

Well i was playing a game i think it overheated im not sure cause its like over 100+ and i was playing games. Anyway there was a screen that was a bunch of colors i think mostly purple or pink but whatever. So i shut down my computer and when i turn it on it makes a buzzing noise for like a minute. I cleaned the inside of the computer all the dust out from the fans and all that but it still makes the sound. Also after the buzzing sound it turns off then back on then a light buzzing sound for a bout 4 or 5 mins then i think its gone. Its either that or because i turn on my modem then turn on my computer a second later.(i dont usually do that).