I'll be replacing the stock AMD Opteron heatsink that looks a little like the XP-90. It is copper based and only uses an 80mm fan, unlike the Silent Whisper which utilizes a 92mm fan.
I used the quick release on the old heatsink and placed it to the side. Then I cleaned the thermal paste off the CPU to prepare it for the new heatsink. As always, you will need to make sure all of the old thermal grease is properly removed from the CPU before mounting your shiny new heatsink. Arctic Silver ArctiClean is an easy and relatively inexpensive way to insure that you've done a proper job of this. Not properly cleaning or applying thermal paste can easily wipe out the gains by installing a new HSF, so this is a very important step.
To install the new heatsink, I lined it up to make sure that it will cover the entire CPU and to make sure that I'm not going to smear the thermal grease everywhere. I then applied the new thermal grease and seated the heatsink over the CPU.
It is important to make sure that the retaining clips are in place and not going to slide off if and when you move the machine. As you can imagine it is never a good thing when they don't stay in place.
Making sure the other side with the locking clip is in place as well.
Take a good look at the way the stock HS and the Silent Whisper locks. I have to say the stock HS looks more stable and feels like it's held in place better. The stock HS has a tab that locks on the retaining bracket whereas the Silent Whisper has a small flat edge that keeps it from turning.