In any dialog box, the OK button enacts the changes you just made to the settings and closes the dialog box.
The Apply button also makes the change, but keeps the dialog box open.
Use The Control Panel p. 4
When the Control Panel is in classic view, you can rearrange and change the size of icons just as you can documents in a folder window. Just go to the View menu and select an option.
Get Dialog Box Help p. 6
Sometimes the help you get in a dialog box is so specific that you can't tell what it means. If you can't find what you're looking for in the Help and Support Center in the Start menu, you can look online. Click the Support icon at the top of the Help and Support Center window. Your Web browser will launch and take you to Microsoft's support Web site.