You should just be able to press down on it while slightly twisting it out. If all else fails, you could CAREFULLY use a screw driver and try to just pop it off the tabs...
The question is why are you doing this If your curious, I beleive the CPU is simply a Pentium III 733 Which, that being said...I don't think that one HS is the CPU... my 733 has one more like the one just off the pic...