White Box On Desktop In Upper-Left Corner Of XP- Certificates Button At The Bottom

I have White Box on my Desktop In Upper-Left Corner of my screen that I cannot delete or otherwise remove. I am running Windows XP, and McAfee and Ad-Aware say I have no viruses. In trying to get rid of this box I have discovered that I can expand and reduce the size of the box from the lower right hand corner, and if I drag a web page shortcut icon from my desktop over the box, the web page is displayed. When a web page is being displayed inside the box there are scroll bars on the right and bottom sides to scroll around the web page. If I click on a hyperlink within the box, my default web browser is opened to the link. At first I was using IE, and then I switched to Firefox, and it made no difference. Periodically, the web page being displayed inside the box will disapear, along with the scrolling bars, leaving behind a white box.

When there is a web page being displayed in the box I can right click on the box and I get a menu with the following options: Back, Forward, Save Background as, Set Background, Copy Background, Set as Desktop Item, Select All, Paste, Create Shortcut, Ad to Favorites, View Source, Print, Refresh, Export to Microsoft Excel, Print, Properties. Some of these items are grayed out. If I select properties, there is a "General" tab with the name of the web page, Protocol Info, Type, Connection, Address, Size, Created, Modified. There is a Certificates button at the bottom in addition to OK and Cancel buttons.