I'm really under impressed by Sierra to date. It has made my entire Mac as slow as a pre 2000 computer. I wish to reinstall El Capitan. How do I do this? I have a iMac 21 inch late 2013 model. Memory is 8GB 1600 mHz.
iMac, Mac OS X (10.6.8), It is actually a Mac 10.8.3
You will need to erase your hard drive and can then restore from your backup you made before upgrading. You use recovery to erase and restore.
It would be a better idea to fix what's wrong, since Sierra should result in a system that runs faster than the same system running El Capitan.
The following will begin to help identify the problem, so that you can fix it.
Back up your Mac if you have not done so already. To learn how to do that please read https://www.apple.com/support/backup/. To learn how to use Time Machine read Use Time Machine to back up or restore your Mac. The reason for creating a backup is that the symptoms you describe could be indicative of an impending hard disk drive failure, so securing your data is a primary concern.
Then, shut down your Mac and restart it in "Safe Mode". To learn how to do that please read: Try safe mode if your Mac doesn't finish starting up. Compare how your Mac works in Safe Mode to how it has been.
Then, restart normally. If the same problem returns, please read the section If an issue doesn't happen in safe mode for Apple's recommended actions.
Finally, you can temporarily create a new User Account, and log in to that account to determine if the problem also exists when logged in to that Account. To learn how to do that read How to test an issue in another user account on your Mac. When you are finished troubleshooting, you can remove the temporary User Account by following these instructions: macOS Sierra: Delete a user or group. Before removing it, confirm you don't need any of the files you might have created in that Account.
Let me know what you determine.
How can I reinstall El Capitan?
