This might seem a stupid question but i just want to be sure.
Some cooler have a backplate with sticky (really sticky!) edge on back of them in order to stick it on the motherboard. I removed mine with a lots of force but at least i removed it.
However, there are some left glue residues on the motherboard.. that would be pain to remove ! personnally i don't really care if they are keep there but it is safe ?
http://cdn.overclock.net/0/0d/600x450px-LL-0dba8363_Pic1.jpeg (sorry the integrated pic fonction seemed to not work i can't see the pic otherwise)