You will undoubtedly be happy with quicker application response times or higher frame rates in games, but why let the extra performance go to waste when you're not using your PC? Distributed computing projects are popular as a way to solve complex or CPU-intensive problems using the power of PCs around the world.
Projects to find cures for cancer, crack encryption, unlock the secrets of our genetic code, and identify drugs to fight anthrax and smallpox, are just a few of the distributed computing projects out there. What makes these projects irresistible is the fact that they track your PC's number-crunching power and total contribution to the overall effort, so you can see how your PC, or group of PCs, stacks up against others.
Performance junkies can even join teams of users running the same distributed computing effort, combining their forces and engaging in friendly competition against other teams. The teams work toward achieving the project's goal and earn bragging rights as a bonus. Learn about six popular distributed computing projects, which can put your new higher-performing PC to work when you're not using it, at http://www.techimo.com/teams.html.
Be warned, however: because distributed computing projects keep your CPU running at 100% effort around the clock, stability problems are more likely to surface. That can be a good thing if you want to find problems and eliminate them, but it can also be annoying if you're happy with your PC's new level of performance and you don't intend to do any further tweaking.