Prior to installation, the CPU IHS and heatsink base were both cleaned with isopropyl alcohol before applying a small amount of Arctic Silver 5 thermal compound. Thermalright provides a nicely illustrated set of installation instructions, which are easy to follow.
(Intel Socket LGA775 mounting hardware)
The first step in the installation process is to insert either the Intel or AMD standoffs into the backing plate. Once the backing plate is positioned from underneath (requires removing the motherboard) two cross pieces bolt on to the top of the stand offs. These cross pieces have tap holes in the center for attaching the heatsink.
The next step is to position the heatsink on top of the CPU (after applying thermal compound of course) and securing it with another cross bar and two shoulder screws with springs. The screws bottom out when tightened so there is no having to guess about how tight to screw them in. A small dimple in the mounting cross bar engages into a hole in the top of the heatsink base to center and hold it in position.
Overall, the SI-128 SE was very easy to install onto my LGA775 test bed. This was a very pleasant surprise since installing some previous large down-draft style coolers proved to a bit of a challenge on this particular motherboard. Clearance is very good around the socket area components and there were no problems with interference. My only minor complaint is that the mounting cross bar does not hold the heatsink base captive so it is free to rotate if you push on it hard enough.
Thermalright uses their classic wire retention clips to secure the fan on top of the cooler along with two anti-vibration strips that mount under the fan. The clips hook into holes on the side of the large upper fin array and loop over the bottom flange of the fan.
This design works great with most fan housings except for the ones that have the area between the flanges filled in solid at the corners, like the Nexus fan I used during testing.
Here is a big Delta SHE air turbine (38mm thick) mounted on top of the SI-128 SE. This bad-boy can really move some air but you may need ear plugs.