The reason as to why your PC is overheating may be because of the following:
Dust may have accumulated inside your PC and therefore making the fan not to perform properly. Or the fan may be faulty. The fan is very essential for cooling the system when it heats up and therefore anything that might happen to it that hinders it to work properly will lead to the system overheating.
The applications that you are running may be memory intensive applications, and especially that they are games and therefore they are exhausting the memory space of the system during their execution and thus causing it to overheat. You may therefore want to remove some applications to free up some memory space or upgrade the memory capacity of your computer.
Gaming in general puts a lot of graphic pressure on system's resources and is considered quite a burden on system performance. However, if you have sufficient RAM, and a reasonable processing power, your system should not get extremely hot. Sometimes there is dust in system that blocks the ventilating pores hence trapping the heat but as you have mentioned before it doesn't seem to be the problem. I suggest that you apply some Thermal paste on the system to create a heat sink for your PC. That normally helps in cooling down the system hence increasing the performance. You can see the procedure in the below video.
Salam Noureen, Be careful using your system because excessive heat can damage your hardware.
If you installed a new Processor try Re-Installing the processor chip and Heat sink ,and also apply some Thermal paste on the top side of processor for better conduction of heat to the heat sink, Check the Fan of processor and working normally, if it is making noise by excessive speed than it is sure the problem of heat conduction try changing thermal paste.
Check the Fan Installed on graphic Card if it is working correctly, If not check its wire connection or change it.
Try installing an extra fan in the CPU Casing for better Air Circulation Because you are playing games with high specifications.
If the Problem doesn't resolve do not boot window because it will burn your Processor or other Hardware.
If your computer doesn’t want to boot or becomes very slow and very hot, it is the result of a failing CPU cooling system. This means your CPU cooling fan is no longer working properly. You just need to replace it with a new one and it should operate back to normal.
If your CPU’s cooling fan is failing, it will not provide enough ventilation for the processor which results to a processor that’s getting hotter and hotter. When the temperature of the processor is rising, it will result to a system that’s becoming slower and slower and will eventually shut down. When your computer turns off, that means the processor has overheated.
You will not be able to turn it back on until the temperature has subsided. To avoid this, just replace the cooling fan on top of the heat sink on the processor to restore the normal operating temperature of the CPU. To help you learn how to buy a new cooling fan for your CPU, visit How to Choose and Mount a CPU Fan.