Just asking, How long have you had that computer?
If the computer is really old then you might have some trouble.
I just did a little reseting of my old computers CPU heatsink and I found a little suprise when i got the CPU and the heatsink out.
I used the twisting method to take off the HSF and then pulled it out, lucky me, the CPU came with it. ^.^
I try to get it off by prying it off with a screw driver and lets just say I almost ripped the Board with all the Pins off.
A few hours with qtips and rubbing alcohol and it didn't come off. Also Scraping the sides of the CPU with a screwdriver to get some thermal compound off.
Got my handy screw driver and a hammer and 5 HARD hits to the side of it and it came off. ^.^
Thermal grease was dried up on the cpu and HSF so it took a while of scraping with my nail and a cloth of alcohol to get it all cleaned.(2 Hours)
And since i scraped my HSF up really bad, I had to lap it.
The rest went nice and smooth. ^.^
All I'm saying is, If the computer is over 5 or 4 years old, be ready to have some work ahead of you.
Not to say its hard to reseat a heatsink, which it isn't, just watch out if it an old computer.(I used a hammer cuz it was only a crapy 1.8Ghz P4) ^.^
Good Luck