Symptom
You have both Mac OS X and Mac OS 9 installed on the same volume. You press and hold the Option key during startup, but only Mac OS 9 appears in Startup Manager.
Note: All Apple computers (other than servers) come in this default configuration.
Solution
You may use the X key during startup to force the selection of Mac OS X. Follow these steps:
1. If the computer is shut down, press the power button. If it is on, restart it.
2. Immediately press and hold the X key. The computer starts up to a gray screen, then restarts again.
3. Release the X key after the computer restarts.
The computer starts up from Mac OS X. The Startup Disk setting is now changed to start up in Mac OS X. This differs from using Startup Manager, which does not save the preference change.
For more information, see technical documents:
106696: "
Mac OS: Press X Key During Startup to Select Mac OS X on Single-Partition Installations"
106698: "
Startup Manager: Only Displays Mac OS X, Not Mac OS 9"
106178: "
Startup Manager: How to Select a Startup Volume"