We don't load a disease, per se
What happens is Stanford want to simulate the folding of a protein. Obviously, simulations are done by computers, but there are so many factors, and it requires so many resources to simulate it correctly, that they'd need a huge supercomputer. So, instead they distribute small parts of that simulation to us. We all do a part of it and return the results, and then they use that information.
It's got advantages over a supercomputer in that it costs less, its actually more powerful, and it allows the public a chance to feel as if they're helping out too.