Some games freeze my system completely

This is completely wrong. A slow computer will just run slowly, that is all. No such thing as crash due to overload (assuming you don't run out of ram and have swap disabled I suppose)

It will hang the system if the OS's scheduler prioritizes it over other things like the UI (i.e., if you set the process priority to High/Realtime.) If you don't do that, something funky is going on, probably. What does Task Manager say before it freezes?

I've never seen that happen on on ne PC's because UI usually runs in separate thread so no freezing on multicore CPUs. (Though insane lagging/ constant no response is still possible)