1. Fine. But there are only 10 Mother Boards
out there that support more than 100GB of RAM. Now the problem comes in that you can not find any RAM modules
that can go into it to give you that amount of RAM. The fact is they come in sets of 3x4GB for a total of 12GB. Even with 18 slots you can get 6 sets. 6x12=72GB MAX RAM that you could get commercially. Well short of the 100+Gb you want.
2. It doesnt make sense to have a VM running if you are in game. What purpose does it serve? None. You could easily suspend the VM and play the game and not have to get a system like this. It is defeating the purpose in so many ways.
3. Yes for desktop versions of Windows that is the limit. Server OS's do not have such a limit but you are limited to what you can do with them as not every game works on a Server OS as it is not made to be used for this purpose. So even if you did install Server 2003 there is no guarantee that the games you want to play will work as it takes a lot of knowledge to get the Server OS to work like a desktop and even then you are still very limited to what you can install as the game itself has to be compatible with that OS. There are tricks but i wont go into detail as that information is not needed.
4. You want to use your current CPU as per your original post. You asked as bkolk pointed out that you were wondering if you could buy another CPU that is the same model as your current one. I mentioned the fact that you would have to use Xeon CPU's cause of this fact that you can not accomplish what you want given the information you gave.
Again all you have to do is check out NewEgg and you will see that what you aspire to do is not possible given the availability of products and their limitations. RAM is going to be the big one as there is no RAM sets out there available to buy by a consumer that will reach the plateau that you want. Then comes in the OS, and the CPU aspect. With all the parts running, there is no way possible that a 600W PSU will run it all. You will need that much just to drive the dual CPU's, RAM. That isnt even taking into account the fact you want to run dual video card. You will need at least 1000W PSU. simply for the fact that EACH video card requires a PSU of around 500W itself. Running 2 of them will require you to have more power.
This is all just information that you should know in order to really think about what you want to do. You never mention a price point. As this is going to run well over $5000 if not more to accomplish this.