While I've actually replaced the NABU fan (since it won't work with 230V mains power), I did spend some time adjusting the screws on the original fan to see if it can actually be done. In my experience it took several(!) goes undoing and retightening the screws before I had it turning freely - hence the "repeat as necessary" comment in the how-to guide!
To avoid frustration you could always replace it with a new fan. I opted for a 'Noctua NF-A8 ULN, Ultra Quiet Silent Fan', which doesn't make the system sound like a jet taking off while still adequately dissipating heat. It also comes with 'noise reducing' clips, which you simply pull through the holes in the case and clip the fan in place, and are a lot less fiddly to install than the nuts and bolts. Then again, wiring a 12v fan to the original PSU might prove challenging....
D.
