ThumbWin adds a new desktop functionality to Windows XP, similar to Vista's ability to show thumbnails of all minimized windows. Once installed, this small tool will generate a thumbnail with the content of every window you download to the taskbar.
These thumbs are especially helpful when you minimize so many applications that you spend too much time and waste too many clicks on finding each one of them.
Using ThumWin, you'll find the right app just by taking a look at the thumbnails.
ThumbWin's settings allow you to select the size of thumbnails along with other details.
Also, they don't seem to hog on resources at all. Bear in mind, however, that they only work if you minimize windows one by one. That is, there will be no thumbnails if you use the "Show desktop" button.