Ok, I found it. It's called Lightbox, it's a wordpress css script.
I managed to make one and put it on my site. It worked with flash... sort of. If you like really really messed up pages.
I should have given you an example of what I wanted. oops.
I managed to find a tutorial on it:
http://www.emanueleferonato.com/2007...script-needed/
So I'm working on adding it to my site. Which it works fine with .png and .jpg. But it's liking flash at the moment.
Any idea if I can use flash with this?