I suspect the images are stored internally, but you can copy and paste them.
Open Tools | Customize, right-click on the button whose image you want to
capture, and choose Copy Button Image. Close the Customize dialog and Paste
where you want the image. Also, see
http://word.mvps.org/FAQs/MacrosVBA/CustomButtonFaces.htm for a download
that contains all the button images used by [some previous version of]
Office.

They are hard coded into the application. You can copy them to the clipboard
from the tools > customize dialog. Then paste wherever you want.
Alternatively you could use a screen capture utility such as the excellent
SnagIt, which is what I use to illustrate my web page articles.

You're best option is to capture a screen shot and use it instead.
SnagIt, by TechSmith
(http://www.techsmith.com/products/snagit/default.asp) is an excellent
screen capture program. It can capture various regions of the window
the mouse pointer, etc. They have a 30-day trial available if you want
to try it out.

Otherwise, you can copy the screen to the Clipboard, paste in Paint,
select the portion of the image you want to use, copy/paste it in your
presentation.

For specific steps:
- Use the Print Screen key on your keyboard (Press Alt + Print Screen
to capture only the active window)
- Start Paint
- Use Edit/Paste the image in Paint
- Use the square Select tool to select the toolbar/desktop icon
- Use Edit/Copy the selection
- Switch to your presentation
- Paste the image

Yes, it is hard coded into a .dll. There are loads of freeware utilities
that you can get that will sour Windows for icons and save them in a
separate file for you to use. Search Google for Icon Editors.