I'm not sure how that makes a difference though. Either way the processor will work on the motherboard right? Whether it is either of the three. I would imagine the problem is between the motherboard and heatsink.
Anyway, check this out. It's supposed to be a very easy installation. I would just make sure you have everything set correctly, and press down the clips gradually. It's compatible with socket AM2 so either you're mounting it incorrectly or just not applying enough pressure.
Edit: Make sure you are putting down the side without the lever first! (as shown in the guide)
This motherboard is different from the others I have seen. Usually they have the three little bumps on the mother board around the processor. What I mean is where the heatsink latches on to the motherboard. On mine there is only one rather than three to line up with the fans three holes. Hopefully this makes sense. I'm not quite sure what the technical term for these are.