My solution was to remove the existing fan cover and fan, and replace it with a 40mm fan, I had one with a 3 pin connector lying around which saved me money but if I hadn't then they are not exactly expensive.
To remove the existing fan:
- 1. Remove the 4 screws holding the fan cover in place, remove the fan cover.
2. Remove the 3 screws holding the fan to the heatsink (You'll have to move the fins around to get access to all of them)
3. Carefully remove the fan after unplugging it from the mobo.
4. (Duh moment) Make sure you've accounted for 7 screws in total.
After removing the existing fan I discovered that I could simply place the new fan on top of the heatsink (You could change the heatsink if you wanted to but for most people the existing one will be fine).
To secure the new fan use self tapping screws just wider than the gaps in between the fins (about 1mm, I used 1.5mm screws) obviously be careful and be sure to hold tightly onto the fan and heatsink so as not to twist it too much while screwing the fan down (this is effectively forcing fins apart and putting a lot of pressure on the heatsink and chip if you are not careful) Also be careful not to let your screwdriver slip of you will have a new mobo mounting hole.
After the fan is secure (2 screws will do but if you can get in the full 4 then all the better, I only managed to get in 3) plug it in, test it and away you go.
Here are a couple of images that may be useful:
Exploded view
All removed parts
The first one is an exploded (rough) diagram of the heatsink and existing fan assembly and the second is a poor quality picture phone pic of the old fan, screws and cover with a ruler for indicative purposes.
The original fan was a truly poor design, it sits inside the heatsink, on top of the heatsink base so that any dust sucked into the fan will congeal around the fan mechanism and eventually clog it up and cause it to become inoperable, also it's tiny size, and fast spinning makes it ineffective and noisy and to top it off the fan cover seems to all but remove the chance of any airflow through the heatsink fins.
Overall a big mistake by Asus and a right royal pain for the consumer.
Anyway I hope I have managed to help someone with this.
Thanks for reading
Take care
Eric