They've soldered on the IHS since the Northwood "C" revision iirc.
To remove the IHS you must get the CPU rly hot, around 55*C+, in windows.
Then proceed to shut down or cut the power and remove the HS/F fast, then cutting around the epoxy. Then repeating the heating up phase, then shutting down, removing HS/F, and slightly lifting on it. Do that again and again and again and you'll successfully remove it