If you have an optical drive connected to your computer, you can insert an installation disc to see it in Startup Manager. Double-click or press the Return key to start up your Mac from the volume you selected.Use your mouse or trackpad, or left and right arrow keys to select the volume you want to use.If you don’t see the volume you want to use, wait a few moments for Startup Manager to finish scanning connected drives. After a few seconds, the Startup Manager appears. Immediately press and hold the Option key.Use these steps to choose a startup disk with Startup Manager: Startup Manager allows you to pick a volume to start from while the computer is starting up. Temporarily change your startup disk with Startup Manager The next time you start up or restart your computer, your Mac starts up using the operating system on the selected volume.

Select your startup disk from the list of available volumes.Click the Startup Disk icon in System Preferences, or choose View > Startup Disk.From the Apple menu choose System Preferences.You may also find files matching programs that are no longer installed these can also be removed.Set the default startup disk You can change the startup disk your Mac automatically uses from System Preferences. This will stop the program from telling macOS it needs to be launched. If you see a file name that matches a program you know continues to launch on startup, you can freely delete it. plist files that may be connected to a certain program or service. Select the Library folder that appears and again look for LaunchAgents and LaunchDeamons folders. Open Finder, click Go, and hold down the the Option key. They may also be separately stored within your computer's hidden files. Open your disk drive in Finder-it's usually named Macintosh HD by default-then open Library and look for folders named LaunchAgents and LaunchDeamons. They can even be used for nefarious purposes. These files are hidden in places you won't normally look and tell the computer to launch programs independently of regular startup items. If you still have certain programs opening when you boot up your Mac, it's likely due to launch daemons and agents hidden within your libraries. How to Set Up Two-Factor Authentication.How to Record the Screen on Your Windows PC or Mac.How to Convert YouTube Videos to MP3 Files.How to Save Money on Your Cell Phone Bill.How to Free Up Space on Your iPhone or iPad.How to Block Robotexts and Spam Messages.

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