why does my computer fan running full speed at bootup?

when i turn on my computer it runs at full speed like jet i already clean those fans 1week ago after hearing those jet sounds but it seems cleaning didn’t help i dont know whats going on can someone advice me?

Hi. Depends on the machine. Some computers have a problem with cooling so the BIOS tells the fan to max out during boot. If it slows to normal after boot I would not worry about it. Best thing to do if find the latest BIOS and flash it. Get a friend if you are not sure how to do this.