Firstly I must point out that I was once one of them. I worked in the computational chemistry labs of one of the world's largest pharmaceutical companies.
Here's the important thing to know: to simulate chemical processes you need to do quantum mechanics. You may have heard of the 3 body problem. Finding the orbits of 3 particles bound in a gravitational or electrostatic field is called the 3-body problem. And it's hard. Well, basically it has no solution apart from throwing CPU power at it. Well that's nothing. It's the most trivial little problem compared to the quantum 3-body problem. It's orders of magnitude harder. But that's nothing. A protein has thousands of particles in it. And get this: each time you add one more particle to the quanum n-body problem it gets an order of magnitude harder. Solving to find how a protein folds isn't just an order of magnitude harder than figuring out how 3 planets orbit. It's many many orders of magnitude harder.
Well, what can we simulate if proteins are so hard? We can do a good job on single particles like a free electron. We can even do a stupendously good job of figuring out what an electron and a nucleus do and so we have great theoretical predictions for atomic energy levels. What about the simplest molecule: 2 nuclei and some shared electrons. Well guess what - the simulations are poor. Very poor. We can barely predict the existence of chemical bonds (in fact I don't think we can at all - I'm just not sure because I'm giving the chemists who claim we can the benefit of the doubt). What about a real commonplace molecule like water. It turns out that we understand next to nothing about water. Just about every physical prediction you'd like to make about water from its molecular structure is wrong (unless you do the standard computational chemist trick of tweaking your parameters after running the failed simulation).
Protein folding isn't going to be solved by getting innocent kids all over the world to donate their CPUs. It'll be solved by some chemist pulling their finger out and figuring out a better way to do it.
So switch your PCs over to seti@home now! It's no less likely to succeed and it's a lot more fun.