Check Out What Windows Explorer Can Do
If you're selecting files one by one in Windows Explorer, it may be helpful to make note of a feature in Windows Explorer that's often overlooked. In Windows Explorer if you go to Tools . . . Folder Options and then click on the View tab, you'll should be able to scroll down and see an option to use check boxes to select items.
This will allow you to select random files for copying or deletion with more ease than if you hold down the CTRL key. The check boxes allow you to easily review what you're doing before you make a big decision about the disposition of the data.