Removing System Board

I have an Inspiron 1440 for which I'm trying to replace the heat-sink. I followed all the directions in the manual to the letter for removing all the components to get to it. I have removed all the screws from the system board and have pried it loose from the case on the sides. However, something appears to be holding it down in the center. I can't see anything that would be holding it, but I don't want to pull too hard for fear of breaking it.

Can anyone think of what else could be holding it? Is something usually glued to the system board to keep it in? Could something have melted? Anything?

Thanks in advance for any input. If more info. is needed, I'll gladly furnish it.