High Sierra download

The circle with the white line diagonal through it is a symbol that your computer displays when there is something wrong with the OS that is installed on it. If your computer is recent, you should be able to press and hold the "Command + R" key right after you turn on the computer before it tries to load macOS. This will get you into the recovery section and you can use that to recover the OS by installing it again. Hopefully you have done a backup and you can recover it from a backup on TimeMachine. If not, you can get it up and going but you may not have any information when it gets going again. If you're really uncomfortable doing this, you can always take it to an Apple Store and see a Genius at the Genius Bar and they can help you though it and get your computer going for you again, but if you didn't do a backup, you may lose all your data.

Teacherprobz wrote:

These are the 4 screens that keep appearing and then screen goes black.

If you aren't able to get into the recovery of your iMac by pressing and holding "Command + R" after turning on your computer, I would suggest you take it to an Apple Store and visit a Genius at the Genius Bar. They should be able to help you out and let you know what needs to be done to get your computer running again.

Those are the options that you have. If you have a Time Machine Backup, you should be able to restore from it, however, I don't know how it will act if it's a backup from a previous version of macOS. If you reinstall the OS, you should get your computer going again, but keep in mind that you are going to lose everything that you currently have on your computer. Getting help online I'm not totally sure how that works as I have never tried that, but I'm assuming that it will let you connect to the Internet using a browser like Safari to search and see what you can do. Most likely bring you back to here. If you don't want to install the version of OS that you have, then you're going to have to download a different version and create a bootable drive to use to install that version and get that version working on your computer.

What crazy things? Please be more descriptive of what the problem is so we can help analyze and provide some suggestions.

With this update 😟 Mac Computer has a black screen with a white circle & white diagonal line in the center of the circle.

I had the same issue, now I have a black screen with a white circle with a white diagonal line 😟

No, I don't think it installed properly, it quit in the middle 😟

I hope it didn't affect my computer too!

I can't use my desktop..I have done the same thing..hopefully some one will respond on how to fix this! $1,300 dollar computer..this stinks! 😟