While nearly all systems have a fan on the power supply, many modern systems have a fan on the front of the case to push addition cooling air over the CPU, a fan on the back to push hot air out of the system, and side or top fans to move additional air in and out of the chassis.
If you suspect your computer is overheating, the first components to check are the fans. Does your computer repeatedly reboot at random or randomly shut down and won't start again for several minutes? There might be several reasons why this occurs, but overheating should be your prime suspect.
