Folding@home is a distributed computing project - people from throughout the world 
download  and run software to band together to make one of the largest  supercomputers in the world. Every computer takes the project closer to  our goals.
  Folding@home uses novel computational methods coupled to  distributed computing, to simulate problems millions of times more  challenging than previously achieved.
Protein folding is linked to disease, such as Alzheimer's, ALS, Huntington's, Parkinson's disease, and many Cancers
Moreover, when proteins do not fold correctly (i.e. "misfold"), there can be serious consequences, including many well known diseases,  such as Alzheimer's, Mad Cow (BSE), CJD, ALS, Huntington's, Parkinson's  disease, and many Cancers and cancer-related syndromes.
What is protein folding?
Proteins  are biology's workhorses -- its "nanomachines." Before proteins can  carry out these important functions, they assemble themselves, or  "fold." The process of protein folding, while critical and fundamental  to virtually all of biology, in many ways remains a mystery.
You can help scientists studying these diseases by simply running a piece of software.