Spinning wheel spins but Mac Book Pro won't boot - got stuck there!- II

Do I understand correctly that the computer will not boot from the SL DVD? Do you have the original installer discs that came with the computer? If so then try booting the computer from that installer DVD.

If you are able to start from one of your installer discs then:

Repairing the Hard Drive

Boot from your OS X Installer disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Installer menu (Utilities menu for Tiger and Leopard.) After DU loads select your hard drive entry (mfgr.'s ID and drive size) from the the left side list. In the DU status area you will see an entry for the S.M.A.R.T. status of the hard drive. If it does not say "Verified" then the hard drive is failing or failed. (SMART status is not reported on external Firewire or USB drives.) If the drive is "Verified" then select your OS X volume from the list on the left (sub-entry below the drive entry,) click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported, then quit DU and return to the installer. Now restart normally.

If DU reports errors it cannot fix, then you will need Disk Warrior and/or Tech Tool Pro to repair the drive. If you don't have either of them or if neither of them can fix the drive, then you will need to reformat the drive and reinstall OS X.

The gray screen at startup can mean a number of things, but if you see the spinning gear below the Apple logo but the machine hangs there then that typically means there are damaged system files. Only reinstalling OS X will resolve the problem. However, if you reinstalled OS X when this problem previously appeared, and now the problem has recurred after a short period of time this leads me to believe your hard drive may be corrupted or could be failing. If you cannot boot the computer from an installer disc then there's a good chance there is some other hardware problem involved. If this be the case then you need to take the computer in for service.

If you can backup your Home folder to another drive, then do that. Then do the following for you main drive:

Extended Hard Drive Preparation

1. Boot from your OS X Installer Disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Installer menu (Utilities menu for Tiger or Leopard.)

2. After DU loads select your hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Note the SMART status of the drive in DU's status area. If it does not say "Verified" then the drive is failing or has failed and will need replacing. SMART info will not be reported on external drives. Otherwise, click on the Partition tab in the DU main window.

3. Under the Volume Scheme heading set the number of partitions from the drop down menu to one. Set the format type to Mac OS Extended (Journaled.) Click on the Options button, set the partition scheme to GUID (for Intel Macs) or APM (for PPC Macs) then click on the OK button. Click on the Partition button and wait until the process has completed.

4. Select the volume you just created (this is the sub-entry under the drive entry) from the left side list. Click on the Erase tab in the DU main window.

5. Set the format type to Mac OS Extended (Journaled.) Click on the Options button, check the button for Zero Data and click on OK to return to the Erase window.

6. Click on the Erase button. The format process can take up to several hours depending upon the drive size.

Wait for the formatting to complete then quit DU and return to the installer. Complete the OS X installation. The Zero Data selection will take time but is sure to fix any bad areas on the drive if there are any. Hopefully this will prevent further file corruption from occurring.

It's quite possible. Many people who upgrade then have problems usually had problems before the upgrade. The upgrade merely made them worse. For future reference:

System Upgrade and Installation Procedure

Basic Caveats

1. Disconnect all peripherals except the original mouse and keyboard.

2. Quit all applications if this is not an installation from an Installer DVD.

3. The installation process should not be interrupted. If a power outage or other interruption occurs during installation you may have to erase the hard drive and reinstall from scratch.

4. Once the installation begins do not use the computer in any way except to reply to dialog prompts or to restart when the installation is completed. This is especially critical during the installation stage known as "Optimizing the System."

System Update Procedure

A. Repair hard drive and permissions.

Repairing the Hard Drive and Permissions

Boot from your OS X Installer disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Installer menu (Utilities menu for Tiger or Leopard.) After DU loads select your OS X volume from the list on the left, click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported click on the Repair Permissions button. Wait until the operation completes, then quit DU and return to the installer. Now restart normally.

If DU reports errors it cannot fix, then you will need Disk Warrior (4.1 for Leopard) and/or TechTool Pro (4.6.2 for Leopard) to repair the drive. If you don't have either of them or if neither of them can fix the drive, then you will need to reformat the drive and reinstall OS X. Note that Disk Warrior will not work on Intel Macs.

B. Clone your existing system to an external Firewire drive.

How to Clone Using Restore Option of Disk Utility

1. Open Disk Utility from the Utilities folder.
2. Select the startup or source volume from the left side list.
3. Click on the Restore tab in the DU main window.
4. Drag the startup or source volume to the Source entry field.
5. Select the backup or destination volume from the leftside list and drag it to the Destination entry field.
6. Check the box to Erase Destination. Skip this step if you've already formatted the drive.
7. Double-check you got it right, then click on the Restore button.

C. Decide upon an installation option.

You have three upgrade options. If you use the Upgrade installation option be sure you have repaired the hard drive and permissions first and made your backup. If you choose the Archive and Install option then you only need to repair the hard drive.

Neither of the above options will erase the disk. Some of your software may not work with a new system. You will need to upgrade those programs. It would be best to do the upgrades to your software before upgrading to the new system version.