That Eliminate White should work in v7. I've used it many times. It's always best to start a new document with a transparent background. There are many ways to do it manually. Here is one. 

Double click where it says backgound in your layers palette to change background to layer 0 (if not already a layer). Use magic wand and click on the white background of the image. Make sure your Contiguous is checked otherwise it will select all the white in your image as well. You might also need to play with your Tolerance depending on if it is a solid white. You can use the Add to Selection and Subtract from Selection. Once background is all selected then hit delete.

I should add that this method works if you have a well defined edge on your image. When you get into images with hair, grass, etc you need a new method.