Timed rollovers are a pushover!  Front Page customises them from the "Hover Buttons" option in the Insert/Active Elements menu. So - from the Insert menu, select "Hover button", and you will see this...

It is now simply a matter of editing the properties in order to replace the button images with images of your own.

First, delete the words Button Text.

Next, choose the Custom button, and you will see this:

Notice that you can play sounds when the button is clicked, or even when the mouse hovers over it (quite neat, but it can also be quite annoying - beware). If you prefer, you can leave the  "Play Sound" options blank.

The Custom Image section is the important one:
Browse to get the images you want, first for the regular image you want displayed, and then secondly for the `mouse-over´ image.  It is very important that the images you choose are the same size. Click OK when you have inserted your image choices.

You will be returned to the previous dialogue box, where there is just one more thing to be done:  Change the Width and Height numbers to reflect the width and height of the images you have chosen.

Finally, click OK,  save, and Preview your handiwork!