WordPress Theme Viewer Plug In/Hack

Where can I find the pop up theme viewer that WordPress has, it is the one where you clck on the picture of a theme and it pops up in a window that is black then a bigger picture of the theme comes up. I was also wondering if anyone could help me figure out how to create a screenshot without the tool bars etc. Thanks in advance to anyone who can help me on this one!

-Heather