Actually that nut isn't soldered at all, I just glued it in place with super glue. Not on the motherboard itself but, on the plastic cover or tape. Aldarxt, definitely true these older Alienwares have a long life time.
Ssj92 the heatsink is from an M18x R2 or R1 as the oem heatsink wouldn't fit. The 18 heatsink would be off center. So, I did modify it a little, like aldaext said the bottom of the heatsink is cut off because it covered the screw hole. Also on the other side of the heatsink, I sanded this portion down with a handheld dremel.
The oem screw hole ports are touching the card, as far as I know but, it's not making direct contact because on the other side of the graphics is some sort of plastic cover, it's not interferring with any circuits on the card.