i wonder how much cows i could run here is my PC Spec.
16 GB Ram Kingstone DDR3
It's all about the RAM, CrossFire uses around 200-250 MB (minimum), so dividing 16 GB would be around 65-81 instances. Note that:processor means managing resources' center, and the GHz is the speed it runs with; video card is what manages graphics' quality and refresh rate, so it's about what your screen can show; internet connection speed (MBs) also matter, in this case, on how much instances you could run without crashing (I personally think, the minimum is 1 MB for each instance, with a ping of 150-200 if you live near the server [lets say, 3000 KM from the server])
Of course, there are some aspects that reduces that number, like internet connection (in this case), OS stability, number of already running processes, viruses, etc. Anyway please read the entire comment, I've already explained it (in a simplified way).