Visual Task Tips is a lightweight shell enhancement utility that gives you thumbnail preview image for each task in the Windows Taskbar, as seen in the upcoming Microsoft Windows Vista. You will need Windows XP to run Visual Task Tips.
It is a simple utility, you just download and install it, with the promise that it should improve your productivity.
I struggled with it for the first week or so because although it is very useful to be able to hover over an item in your task bar and see what it is, it sometimes freezes applications so you have to click them three times instead of once in order o give that window the focus.
The thing that made it work better for me though was when I discovered that if you hover your mouse over the little visual task tip you can increase or decrease its size by rolling your mouse wheel. This means that the task tip is much less intrusive but you can still make out the contents of the window.
This is a screenshot of the latest version of Visual Task Tips. You can download a free copy from Visual Task Tips