How to Unlock an Image Before Opening it on a Mac
When you run into a series of locked images on a Mac, unlock them before opening them in Photoshop by using the Get Info keyboard shortcut—Cmd+I. Remove the checkmark from in front of Locked on the screen that appears. You may need to enter your administrator password to make the change. Also, at the bottom of the Get Info screen, confirm that you have Read and Write next to your name. If not, toggle the setting to Read and Write.
How to Remove the Read-Only Property on a Windows computer
Images copied from CDs have a read-only attribute. To remove it, copy the file to your Windows computer. In Windows Explorer (File Explorer in Windows 10), right-click the file name, select Properties and uncheck the Read-only box. If you copy an entire folder of images from a CD, you can change the read-only property on all of them at one time by changing the folder’s properties.