yasamoka attach the fan to 5V PSU output, or attach to 12V and 5V rather than 5V and GND to get 7V. Other than that, try the fan on a different connector, and see what happens. Check the capacitor above or beside the fan connector too.
AvoK95 I modified a Molex converter I found and used this guide and installed a Pot. Now I can play with the speed as I want :)
