Microsoft has been doing a better job of this with the release of SP2, but there are still numerous unnecessary Windows services and processes running by default on most PCs. If you'd like to see how many there are just perform the three finger salute (CTRL-ALT-Delete) click Task Manager and then the Processes tab. All of those applications, services, processes, etc. are operating in the background on your PC. The problem is that many can actually open access to your PC to the outside world without your knowledge or active consent. That access is usually justified for what the process is supposed to be doing, it is just that many times your PC doesn't need that process at all—Web servers, network messengers, debuggers—are all processes you probably don't need on your personal PC. (Check out this TechRepublic download for an in-depth examination of these services and for some suggestions for which can be deactivated.)