I haven't tried this in Photoshop elements 2. This works in Photoshop CS2 and I imagine it just about the same with all the photoshop programs.

1. Open image in photoshop.
2. From your top menu: Select > All
3. From your top menu: Edit > Stroke
4. Pick the color border you want
5. Pick the size (pixels)
6. Click OK
7. From your top menu: Select > Deselect
8. Save it.

If the border is too small, increase the # of pixels. You can also change it to in (inch scale).

If unsure how to change color (in step 4) - simply touch the color and you'll get the idea.