How to Remove Motherboard to install CPU fan brackets?

Breaking the x51 down to the motherboard was extremely easy. However, Is the motherboard secured down with mounting tape? I unscrewed the 4 mobo screws and noticed it wasnt pulling up off the case, there was  a lot of resistance. I noticed there is some type of mesh foil around the back of the ports,i used my judgment and did not go any further and decided to come here for some input,  is the foil type mesh securing the motherboard in?

I ask this because I am/ was trying to install a noctua low profile CPU fan I have around from an old PC. I noticed the specs were right and it would fit in intel 115x board range which the x51 falls under if I am correct its an intel 1155 H61 , but i need to get under the motherboard to install the brackets for it. I recognize the fact that this isnt recommended but the alienware x51 is promoted as being fully upgradable and I also take note that the CPU fan is designed for maximum air flow out of the case. But I want to see how much can actually be done with this machine as do others. And I am fully aware that this may/will void my warrenty. All risks I am aware of and willing to take.  Also, I realize the GPU is promoted to mainly support 9 inch GPUs but i also saw some extra leg room before the riser card actually wont go any further, possibly to a 10.2 inch maybe? 

I already installed an intel 320 series ssd into it, so I am aware of how to open it up and put it back together again...Just this motherboard input would help out. 

So, can I please have an answer/ some more input on how to lift the motherboard up off the chasis to install the brackets and install this fan?...

Thanks....