IMAC Updated OSX, now computer will not turn on?

try reinstalling using a different hard drive.

Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
When the menubar appears select Terminal from the Utilities menu.
Enter resetpassword at the prompt and press RETURN. Follow
instructions in the dialog window that will appear.

Insert the Mac OS X installation disc into your computer's optical drive (or an optical drive connected to your computer), and then double-click the Install Mac OS X icon.

Note:If you're using another computer's optical drive, make sure your computer is set up for remote installation, and then go to step 3.

In the Installer, click Utilities, and then click Restart.

When the Language Chooser appears, select your language, and then click the Continue button (looks like an arrow).

In the Installer, choose Utilities > Reset Password.

Follow the onscreen instructions to change the password.

Thank for contacting Fixya, I will be glad to assist you.

Here are some steps you can try to resolve the issue:
• First, hold in your power button for approximately 10 seconds to do a hard shutdown.

• Once your Mac is shutdown, you will need to perform what is called a PRAM reset (Parameter RAM)

• Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously .

• Turn on the computer.
• Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.

• Now, hold the keys down until the computer restarts and you hear the startup sound for the third time.

• Release the keys and allow the Mac to start up.

• Please update me to let me know if this works.

Thanks.

-The MacTechTrainer

Restart from the system disk of the system you want to install. Put the disk in the drive then start up with the C key pressed down until a screen appears. Install system from there.

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Try resetting the Pmu.

1. Shut down the computer.
2. Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
3. Turn on the computer.
4. Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
5. Hold the keys down until the computer restarts and you hear the startup sound for the second time.
6. Release the keys.

Good luck

there is the single user start-up, which you were thinking of. There is also a safe-boot for macs.

To start up into Safe Mode (to Safe Boot), do this:

1. Be sure the computer is shut down.
2. Press the power button.
3. Immediately after you hear the startup tone, hold the Shift key. The Shift key should be held as soon as possible after the startup tone but not before.
4. Release the Shift key when you see the gray Apple icon and the progress indicator (looks like a spinning gear).

During startup in Mac OS X 10.4 or later, you will see "Safe Boot" on the login window, which appears even if you normally log in automatically.

During startup in Mac OS X 10.2 through 10.3.9, you will see "Safe Boot" on the Mac OS X startup screen.

To leave Safe Mode in any version of Mac OS X, restart the computer normally, without holding any keys during startup.

Sony Digital camera DSC-T200 will not download to my computer and I would like to downloading to my computer

You can dowload the the driver here: ftp://ftp.agfa.be/DRIVERS/softpack/scanners/Mac/ScanWise/OSX/ScanWise_SnapScan_1212u.dmg.sit

Regards
Hands of Time