[shane0123]

So I add a new hard drive without cloning the old one to it. I went in to disk utility and tould it to boot from the new disk. This does't work so I need to know how to tell it how to boot up from the old disk and not the new one. Tried the options key at start up but it on shows old disk and the computer keep running and will not let me click on anything, What can i try next?

[P]

Are you using a wireless mouse or keyboard? Try using a wired mouse and keyboard to select the correct disk (you can use the mouse and doubleclick or use arrow keys and return).

[seanc]

Have you installed an OS to the new hard drive?

[Chito]

IIRC start up while holding down the option key will get you to the boot panel, all of your available startup disk options will be listed there.

[chris v]

I have to wait a loooong time after doing the option-key-to-choose-an-OS thing before, like 4 or 5 minutes while it looks for drives, even after a couple show up.

Alternatively, If you pull the new drive back out, it'll boot from the old one after a sec. You'll see the flashing question mark folder for a few seconds, then it'll detect the drive that's still there. Change your prefs back, then re-install the drive.

[angelmb]

Holding down the X key during startup would force the system to boot into OS X.

If that doesn't work, insert the Mac OS X Install disc and hold down the C key to boot up from the Install disc. It will take longer than booting up from the hard disk, but you would be able to choose the start up disk going to the Tools (IIRC) menu.

[Waragainstsleep]

Its Utilities menu -> Startup Disk.

Failing that, disconnect the cable from the new disk, then choose Startup Disk from the Apps -> Utilities folder once booted and choose the old drive as boot drive. Then you can reboot and reconnect the new one. Like Chris said.

[MacCompuFix]

If the system will start, you need to go into the System Preferences and select the Startup Disk icon then select the disk you would like your machine to start from.