Take the fan to a bench and apply power to the fan. If it does not spin, it's dead.
Sorry if this is too basic for some. But it's a simple bench test that I've done too many times.
Yesterday everything was fine, today my PC shut down without warning 2 times, so I took a closer look inside and noticed my Scythe Katana 3 CPU Fan that I used to cool my AMD Phenom 9950 is not even trying to spin. It's barely a year old, and that it does not even try to spin up strikes me as very weird. Nothing has changed since yesterday that I am aware off.
I'm using the MSI K9A2 KF-F as my motherboard and the Be quiet! Dark Power Pro BQT P9-550W is my PSU. Is there still anything I could try before I go buy a new fan? Like I already said, that it would just stop working without giving a fight strikes me as very unusual and makes me doubt whether it is really broken or not.
Help would be much appreciated. Wish you all a nice and hopefully trouble free weekend.