I have no idea. The computer is an acer with intel. But I know it is not an intel heatsink (775)
So let me make sure I have my facts correct. The computer is a stock Acer with a stock heatsink on it. Correct?
Yes, everything is as it was when it came out the box, but I am fairly certain that it is not a stock intel heatsink:
http://i1216.photobucket.com/albums/dd368/mellor303/01012008098.jpg
Oh and here is an image of the backplate, it looks fixed on to me.
http://i1216.photobucket.com/albums/dd368/mellor303/01012008101.jpg
No it's not a stock Intel heatsink - it's a stock Acer heatsink. Don't try and reuse it if that's what you're trying to do. It's garbage. And yes, the backplate is fixed to the board.
I wouldn't wait to test out your new motherboard. You want to know if something is defective right away for warranty purposes. I would put the old heatsink on you have now and test out the motherboard.