If you're running a game straight after booting your PC, you might expect the game to run without any problems. However this is unlikely to be the case as you will find by checking Task Manager (right-click taskbar, select Start Task Manager) that many processes are running. Some of these might be server processes, for instance, or other services that use vital resources.
While Game Fire is the best choice for managing this, you might also consider running through the processes and stopping them yourself. This is really a task for advanced users to tackle, although the same effect can be gained from using the evergreen End It All 2.0 utility (available from Softonic) which enables you to "bulk close" any processes that are slowing down your PC, and by extension your gaming experience.