How to build a supercomputer with multi-computers?

not really a good thing to do for a couple reasons. first, most programs do not even take advantage of multiple cores on the same computer, let alone multiple computers. second, even if there was something out there would likely slow down the whole process, because of bottlenecks like FSB and ram speed in consumer computer products. when you hear about supercomputers, they are only useful in running specially designed programs, written specifically to split processes among these computers. they do not run windows or any other home OS

there is not a particular classification, that is effective or it is not. Supercomputers are utilized in industries, no person has a supercomputer. besides, theses specifications are not so ideas-blowing, the GPU is many years old and the processor is between the weakest i7 available, or maybe there, its not area of the 2nd technology i7. A "own supercomputer" could have a Sandy Bridge i7 2600K or a i7 980X (hexacore, btw), and a crossfireX of an HD 59xx, HD68xx or HD69xx or an SLI of GTX 580s.

What you're asking about is called a 'beowulf' - It's a computer made from multiple motherboard/cores. Windows does not support this, but there are quite a few Linux distros that support this. Once the OS is properly configured, it will look like one computer to the outside world.