Need Help with Tricky Mouse Over

Hey guys, I’m currently developing a website and I was given a png image to use for the navigation. I want to have an action occur when you rollover a certain part of the image then a word shows up on top(another png). I’m trying to figure out the best way to do it and trying to figure out if there’s any easy way besides using hide all and show with java-script.

Any clues? Basically I need an image to appear on top of an image with a rollover function.

Thanks for any help.