Cooling with a Noise Control Silverado

[Iron Prophet]

I recently got a noisecontrol silverado which is a quite interesting heatsink. The fan itself runs at some really slow speeds around 3000rpm if I remember correctly. It has a silver base plate which attached to the rest of the heatsink which is aluminum. For some reasons though my 1.33 ghz 266fsb T-bird is still running at around 50°C at max load. I'm using Artic Silver 2 as my thermal paste. Is there anyone with advise to what I can do to help drop my temps?

[Valid]

Did you lap the bottom of the heatsink? Also, what board are you using? It is possible that the measurements given by the board are slightly higher than what the true temperature is. I'm sure someone knowledge with your board will be able to tell you for certain. Also, how is your case air flow?