Screen capture is something I never really think about until I need it. I was recently working on a project and needed to email a screen shot of the application, including the tooltip I was seeing. I've always been a big fan of Alt+PrintScreen to capture my active window, but in this case, I couldn't capture the tooltip along with the window. After a few minutes, I turned to my favorite search engine to see if there was some utility I could use to get what I needed. Amazingly, the perfect utility was already installed on my Windows Vista machine! I found this blog which showed me how to use the Snipping Tool to capture popup menus and tooltips on any window I choose.
To find this tool in Vista, go to your start menu and type "snipping" in the search box, then choose the "Snipping Tool", or you can navigate there yourself by going to the Accessories menu. Now you can choose the snip type you want and set the options, such as having the selection ink shown after snipping.

But what about capturing those popups? Having to click on the snipping tool sort of defeats the whole purpose, right? There's a shortcut for that! To freeze the screen exactly as-is, popups and all, make sure the Snipping Tool is running, but not active (click Cancel or hit Esc to get out of snipping mode), then hit Cntl+PrintScreen. That will activate the Snipping Tool, and you can select a rectangular,window, or other snip type to capture your popup in action.
For example, to capture the tooltips from my Start Menu, I hover over an item, then use Cntl+PrintScreen to start snipping. I select a new Rectangular Snip and choose my selection area, and that's it! I can capture the tooltip along with the menu!

My only wish is that although you have a pen in the Snipping window to draw on or highlight part of your selection, it would be nice to have an ellipse tool to draw clean pretty circles around items of interest. The Snipping Tool is undoubtedly not as fully featured as programs like
SnagIt, but for a simple utility that comes with your operating system, it works well.