

If no checkmark is displayed next to Align to Grid, click on it: a checkmark will be added (and visible next time you look at the submenu), and Windows will immediately re-position the icons on your desktop to align to the invisible grid. Look at the Align to Grid menu item: if Windows XP displays a checkmark icon next to it, this means that Align to Grid is currently enabled, and guiding the alignment of files and shortcuts on your desktop.

To check if Align to Grid is enabled, or to turn on Align to Grid, right-click in an empty area of your desktop to show the context menu: then click on Arrange Icons By, and a submenu will open.
