I mean a fan fan. Like one you put in a room and set it to spin around. My computers been getting awfully hot lately, its summer here so its about 30 degrees in my room (Celsius)
My processor is running at around 55 degrees. Got a blue screen of death, although I'm not entirely sure it was related to heat. I wasn't looking at the temperature when it died. It still is running fine. 55c is pretty high to me, even though my GPU idles at 60c and loads at about 65c
Having the side of the case off does NOT help airflow through the case. The usual arrangement is front [and side] intake, rear [and top] exhaust. This creates a nice flow over all the components in the case, and is sufficiently balanced so that the PSU (always an exhaust) is not fighting against too many other exhaust fans for its air. Opening the side gives all fans free access to air, but disrupts that flow over and through components (other than the PSU).