If you need to remove the heatsink from the Processor, then it is really not that hard to do. You just have to be careful to do the proper steps in reseating the hieatsink after you replace the PS.
The heat sink may be attached with a sticky pad of thermo compound. This is common in factory built computers. After unhooking any screws that hold the heatsink in place you may have to use a slight bit of force to twist the heatsink off. You will have leftover pieces of thermo pad left both on the heatsink and the processor. Now is the time i will use a somewhat used razor knife blade to carefully scrape of as much of the thermo pad as possible without doing any damage to the CPU( don't catch any edges). Some people play it extra safe and use a old credit card to scrape off the old thermopad. Then you clean the heatsink and processor with some isopropyl alcohol. Do a very good job here so the new thermopaste you put on covers the whole area. Now i put a BB sized drop of paste on the CPU and use my finger in the end of a sandwich baggy to spread the paste evenly on the CPU surface. On newer Intel CPU's it may take some more paste than a bb sized one. Then i spread a very thin layer on the heatsink bottom and install the heatsink on the CPU and lock it down with the screws that usually come with the heatsink. Take your time here and be careful that everything lines up and feels good. Now. you are done.
Heres are some good links with pictures. http://www.smartcomp...r...2.asp&guid= http://www.crazypc.c.../hsfinstall.htmhttp://lifehacker.co...-cpu-158363.phpPCMech tutorial for a intel 775 CPU
-Rotate all four of the tabs using a flathead screwdriver.
-Then pull up on the tabs (you wont have to pull them up with much force, the pressure against the mobo was released when you rotated the tabs)
-Pull up on heatsink fan.
-If you plan on re-using the HSF you just removed, rotate the tabs back to the factory position.
-The pre-applied thermal pad is now destroyed.
-Get some high-purity iso alcohol and a lint-free cloth (not anything fuzzy). Apply a little alcohol to a part of the cloth.
-Clean off the grease off bottom of the HSF with the cloth. Dont scratch it! The grease should just buff out with a circular motion.
-Now, you'll notice the CPU has grease on it too. Remove the CPU from the mobo. Place the plastic pin protector back on the CPU.
-Hold the CPU with two fingers. With the other hand, clean off the grease just as you did with the bottom of the HSF.
Installation the second time with thermal grease
-After you have cleaned everything (see 'After-Removal Prep'), buy some thermal grease. This comes in a small tube and shouldnt be more than $10. Good brand is Artic Silver.
-You can also buy official thermal grease from intel here.
-Install the cpu in the mobo.
-Put a little, uncooked grain-of-rice-sized amount of grease on the center of the CPU. It doesnt take much. If your using thermal grease from intel, dispense all of the contents!
-Dont use the spreader, this way I'm explaining works best for 775.
-Install the HSF like normal (see 'Installation the first time')
-Once the HSF is attached, rotate it slightly 1 or 2 degrees a few times. You'll bearly be able to do this. This will spread the compound to the whole surface.
-This way I just explained doesnt seem like it would work, but trust me, it does.
-Hope everything worked for you. The stock intel HSF can be very hard to install, just read customer reviews for any retail 775 cpu, especially if it's your first time.
-There's a video here http://www.intel.com...ence/100617.htm
of someone installing the CPU. Its good, but I disagree with two things he did. First, its a lot easier to install the HSF with the mobo outside the case! Second, one must press the first tab, then the tab diagonal from it, not next to it.
-Here's a tutorial with pictures of installing the HSF.http://www.hardwarez.......cid=19&pg=4