Q: Loading OS on my apple MacBook Pro machine switched off to install and switched off again, it will not pass my sign in but I can get in as guest

Hi ,peterfromsouth normanton,

I understand you updated the operating system on your MacBook Pro, but now cannot log into your user account.  What version of OS X are you running?  First, disconnect any peripherals attached to your computer with the exception of a mouse or keyboard.  Then, try starting up your computer in Safe Mode and see if you are able to login to your user account.

Try safe mode if your Mac doesn‘t finish starting up

If your Mac restarts or shuts down in safe mode

If your Mac automatically restarts in safe mode, OS X might have found an issue that it's trying to fix. 

Safe mode performs a directory check of your startup disk, similar to what happens when you choose to verify or repair a disk using Disk Utility. If OS X finds an issue, the directory on your startup disk is repaired and your Mac restarts. 

If your Mac turns itself off when you start up in safe mode, check the power connection on your Mac to make sure it's plugged in securely at both your Mac and the power outlet. If you're using a MagSafe power adapter, make sure the LED on your power adapter is yellow or green. Then, try starting up in safe mode again.

If your Mac repeatedly restarts or shuts down during safe mode, contact Apple Support, or consult with an Apple Authorized Service Provider or Apple Genius for more help.

What is safe mode?

Safe mode (sometimes called safe boot) is a way to start up your Mac so that it performs certain checks, and prevents some software from automatically loading or opening. Starting your Mac in safe mode does the following:

• Verifies your startup disk, and attempts to repair directory issues if needed
• Loads only required kernel extensions
• Prevents Startup Items and Login Items from opening automatically
• Disables user-installed fonts 
• Deletes font caches, Kernel cache and other system cache files

Together, these changes can help resolve or isolate issues related to your startup disk. 

Starting up in safe mode

Follow these steps to start up into safe mode.

1. Start or restart your Mac. 
2. Immediately after you hear the startup sound, press and hold the Shift key.
3. Release the Shift key when you see the Apple logo appear on the screen.

After the Apple logo appears, it might take longer than usual to reach the login screen or your desktop. This is because your Mac performs a directory check of your startup disk as part of safe mode.

To leave safe mode, restart your computer without pressing any keys during startup.

If you don't hear a startup chime after pressing the power key, see what to do if your Mac won't turn on.

If you are able to start your Mac, but can't access your user account, try resetting the password.

Change or reset a user account password on your Mac

Take care,