Need some help with Windows 7 – taks bar issue

When I used to put my cursor on an Icon on the task bar , any applications that were open under that icon would appear as a picture so I could easily tell what folders, windows were open. For some reason, now when I pout my cursor oveer the icon all I see is test info regarding the oipen applications. For example, If I plcaed my cursor over the Internet Explorer icon and had hot mail open I would see the text “Hotmail.com Windows Internet Explorer”. Can alone tell me how to get back to the original default view?