http://www.microsoft.com/office/previous/tips/visio2000.htm

Create Custom Stencils in Visio 2000
From Brian Lema, Nepean, Ontario, Canada

You can make your own Visio 2000 stencils by doing the following:

1. On the File menu, point to Stencils, and then click New Stencil.
2. Right-click the title bar of the new stencil, and then click Save As.
3. Save your stencil in the Solutions folder in C:\My Computer\Program Files\Visio. (This is the default folder for Visio stencils that automatically opens when you click the Open Stencil button on the Standard toolbar.)
4. Once you name your stencil and click Save, a Properties dialog box will open, where you can customize the stencil by filling in the subject, description, and other details.
5. To populate your stencil with the shapes you want, click the title bar of the stencil where the shape you want is stored, right-click the shape, and then click Copy.
6. Click the title bar of your new stencil, right-click in the empty green area below your stencil, and click Paste.
7. Repeat steps 5 and 6 as needed to complete your new stencil.