After system crash, system password does not work

Reinstall Snow Leopard without erasing the drive

1. Repair the Hard Drive and Permissions

Boot from your Snow Leopard 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 Utilities menu. 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 click on the Repair Permissions button. Wait until the operation completes, then quit DU and return to the installer.

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.

2. Reinstall Snow Leopard

If the drive is OK then quit DU and return to the installer. Proceed with reinstalling OS X. Note that the Snow Leopard installer will not erase your drive or disturb your files. After installing a fresh copy of OS X the installer will move your Home folder, third-party applications, support items, and network preferences into the newly installed system.

Download and install Mac OS X 10.6.8 Update Combo v1.1.

Since she is currently running Snow Leopard you must use the discs that came with the computer unless it came with Snow Leopard 10.6.2 or earlier in which case you can get the Snow Leopard retail DVD:

You can purchase Snow Leopard through the Apple Store:Mac OS X 10.6 Snow Leopard - Apple Store (U.S.). The price is $19.99 plus tax. You will be sent physical media by mail after placing your order.

After you install Snow Leopard you will have to download and install the Mac OS X 10.6.8 Update Combo v1.1 to update Snow Leopard to 10.6.8 and give you access to the App Store.

If this isn't the case, then you need to tell me what version of OS X came pre-installed originally when the computer was new. If it came with Lion or later then there are no discs. She can re-install as follows:

Reinstalling OS X Without Erasing the Drive

Boot to the Recovery HD: Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears.

Reinstalling OS X Without Erasing the Drive

Repair the Hard Drive and Permissions: Upon startup select Disk Utility from the main menu. Repair the Hard Drive and Permissions as follows.

When the recovery menu appears select Disk Utility and press the Continue button. After Disk Utility loads select the Macintosh HD entry from the the left side list. Click on the First Aid tab, then click on the Repair Disk button. If Disk Utility 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 Disk Utility and return to the main menu.

Reinstall OS X: Select Reinstall OS X and click on the Continue button.

Note: You will need an active Internet connection. I suggest using Ethernet if possible because it is three times faster than wireless.

Alternatively, see:

Reinstall OS X Without Erasing the Drive

Choose the version you have installed now:

OS X Yosemite- Reinstall OS X

OS X Mavericks- Reinstall OS X

OS X Mountain Lion- Reinstall OS X

OS X Lion- Reinstall Mac OS X

Note: You will need an active Internet connection. I suggest using Ethernet

if possible because it is three times faster than wireless.

You can ignore that and similar messages: Mac OS X- Disk Utility's Repair Disk Permissions messages that you can safely ignore.

Here is something you can try, then. I am not the author of this:

Pre-Lion/Mountain Lion – Forgotten OS X Password

Type in the following:

The first two commands will depend on your release of Mac OS X. Look at what is typed out in the console to determine the exact format.

Type the follow two instructions to access the startup disk in read/write. Press return after each command.

/sbin/fsck -fy

/sbin/mount -uw /

cd /var/db

pwd

List all files. The l is a lower case L.

ls -al

The move command acts as a rename command in this format.

mv -i .applesetupdone .applesetupdone.old

Reboot your mac

shutdown -r now

Once you've done that the computer reboots and it's like the first time you used the machine. Your old accounts are all safe. From there you just change all other account passwords in the account preferences!!

User Limnos adds detailed explanations:

http://discussions.apple.com/message.jspa?messageID=8441597#8441597

The above the idea came from a post by JoseAranda on September 9, 2006 at 3:48 AM:

http://www.askdavetaylor.com/how_do_i_reset_my_mac_os_x_admin_root_password.html

You will need to scroll down to see this post. Search for applesetupdone

This method is mentioned in an apple support page without giving an explanation.

Once you have a new administrative account, you can change the password of your old administrative account in Accounts preferences in System Preferences. You can transfer your data from the old account: Transferring files from one User Account to another.

You must boot into Single-user Mode. Please review the information and links carefully before proceeding. Be careful what you type on the command line since it's easy to make a typo that can make matters worse rather than better. Before you do anything with the above, you could try this:

How to Create a New User Account if You Cannot Access Your Admin Account

Reboot the computer. At the chime press and hold down the COMMAND-S keys to start into Single-user Mode.

You will boot to a black screen with scrolling white text, release the keys and wait for it finish.

Enter the following lines at the command prompt pressing RETURN after each:

mount -uw /

rm /var/db/.applesetupdone

reboot

After you reboot the computer you will be taken to the Setup Assistant. When you get to the point where you are asked to setup your new user account, create a new admin account. Be sure to name this user account something different than the admin user account that already exists on the system. When you finish the Setup Assistant, it will automatically log you into the new account.

You can transfer your files from the old account to the new one. See: Transferring files from one User Account to another. Once you have moved all your files into your new account, you can delete the old account using Accounts or Users & Groups preferences.