To answer your questions:
1. Yes you're correct. There is no way to enable only 2 cores on S5000VSA. But why would you do that?
2. Windows 7 is not validated on S5000VSA. See Tested operating systems. Personally since Windows Server 2008 R2 is tested as "Installation Only", most likely you can also install Windows 7, but you're doing it on your own since if you encounter any issue you won't get support from Intel.
3. No S5000VSA only supports legacy PCI-32/33 video card like ATI RADEON 7000, as it doesn't have a PCI-E x16 slot.
Thanks for the helpful information, Edward
I actually want the ability to manually select 2 out of 4 cores. So, the S5000XVN will not work for me. You suggested the S5520SC, but it has extra capabilities that I do not need. I prefer the S5500BC.
The S5500BC does allow enabling only 2 cores.
For the following platform,
server motherboard: S5500BC
I have the following questions.
1. Can Windows 7 Professional (64-bit) be installed on the aforementioned system?
2. Will the board support high-performance graphics cards like the ones from NVIDIA?