Or you can assign the affinity timing of the sound system to CPU-1. If Windows is set up correctly and the dual core hotfix applied right, it will always boot any 3D application using only CPU-0, which is the correct way to run games smoothly in WindowsXP on dual core processors. Windows VISTA will however be different.
By assigning CPU-1 affinity to all audio processes (or any other program being run with FS9 or FSX) FSX or FS9 will never see a single hickup from any audio bus time or process and you can take full advantage of a dual core processor with games.
Most people asume because a game is not multi-thread, running a dual system is a waste... far from it