I had to remove a heatspreader from RAM so that it fits into my small form factor workstation. I removed it easily by putting the RAM in the oven at the lowest setting. I didn't leave it there long, the oven temp barely reached 200F.
When I removed it from the oven, it was far too hot to work with using bare hands. I ended up using oven mittens then slowly using a plastic grocery membership card as cover against the PCB and heatsink while I slowly twisted a screwdriver. It came off with no effort. The heatsinks did have a tab-lock on the edges so of course, before heating those were unhinged.
I was so suprized and happy at how easy it was, I called the future better looking over and got yelled at for using the oven mittens. Funny, I swear I'm the one that bought the mittens.