<< Word is that you need to bend the clips.
I just removed the fan, got out a proper sized screwdriver, drank that, and proceeded to convince myself I had just crushed my CPU. >>
LOL
seriously, take off the fan (but if you take off the grill to replace the fan, REMEMBER to put it on the right way or your fan won't spin and you'll get temps over 63c). after bending the clips a lil bit, clip it to the side on the top of the slot (the side with the handlebar's joint is), then, with a screwdriver, place the whole shaft (the metal pole) of the screwdriver against the whole top of the clip of the heatsink gradually but firmly while pulling the other clip out so you can just slide it in its side. pretty easy, after trying a lot of other ways to get the damn thing on for 15 minutes! 😉
for my experience, do NOT press down on the heatsink clip with the end of any screwdriver. it will always slip out and you'll wind up stabbing your motherboard.