Hi @kingducrat
Do you mean the heat sink and thermal pad that covers both the GPU and the CPU?
You may have to screw all the screws back in again and then unscrew the screws in the order as described on p.42 of the [http://h10032.www1.hp.com/ctg/Manual/c06446633.pdf|maintenance and service guide] for the laptop.
There must be a reason why they have to be removed in a set order otherwise it wouldn't be mentioned in the manual.