Missing images is a well known problem with Internet Explorer. I've come across it with IE3, IE4, IE5 and IE6. (I've never used IE7 for any length of time but, knowing Microsoft's inability to fix long-standing problems, I wouldn't be at all surprised if it still happens)
The problem can sometimes be fixed by visiting the Microsoft website and spending hours locating and downloading all of the latest software updates and patches. On other occasions I've had to resort to re-installing Windows.
A far, far better solution is simply to switch to a decent browser. The majority of the 'regulars' here in AB's Technology section use Firefox:
http://www.mozilla.com/en-US/firefox/
The reason I switched to Firefox, several years ago, was that I was fed up of the recurring problems of missing images in Internet Explorer. Since switching, I've never encountered the problem. (Additionally, pages load much faster in Firefox and the program offers far greater flexibility).
Chris