By default, Windows XP uses its own image preview tool if you double-click an image file. Annoyingly, though, other programs will sometimes take over so double-clicking an image opens that program instead. if you'd prefer to go back to the preview tool, open the Control Panel, then choose Folder Options. Select the File Types tab, scroll down to find the file type in question, such as IPQ for Ipeg images, and click the Restore button.