The first time I played Company of Heroes and my charger was plugged out, I was notified that the battery was low, and plugged in the charger, while I was already playing Company of Heroes. After some time my system shutdown, like abnormally. Normally if its battery is charging low then it hibernates. I think it was because it was so heated up? I don't know; what I want to know is can I play Company of Heroes on HP Probook 4520s any longer or should avoid it?
Try running it windowed so that you can keep a closer eye on the thermometers, or set alarms. Laptop max temperatures can vary wildly, so look up the specifications document for your laptop and see what the CPU's rated temperatures are. I did some checking and one of the processors your laptop might have has a rated max temperature of 105 C, but generally anything over 90 C is something to be cautious about.
Be sure that the vents aren't being blocked by things like blankets or pants when playing as well, which can cause rapid heating when the CPU is highly loaded.