there should be a metal clip that goes through the HSF and it attach's on 2 sides of the socket on one of the clips there should be a little piece of the metal clip that has a piece cut out and bent out a little this is a place so that you can stick a screwdriver [regular] blade in and apply a little pressure downward and pull away from the CPU at the same time and it should disconnect it for you. be careful not to slip with the screwdriver or you could really mess something up, its best to take your PC and lay it down so that the MB is flat on the ground when doing this use a little caution and you should be fine. do not put any pressure on the Heatsinkfan as you do not want to crush the core of your CPU.
OH i almost forgot dont use a magnetic screwdriver.
yeah, gently use a screwdriver, i have to do it for my celey stock. Just don't do what i did to remove a fop i had attached wrong, i used a dremel to cut the tip(the board was doa, so no biggie although i got the shards removed).