Bought a pc off of a friend who to be fair did warn me that the psu (Coolermaster m520 I think) made an annoying whirring sound. However I used the pc fine without any noises for a week, and suddenly I switched it on yesterday and it constantly makes a buzzing/whirring sound. It is the fan on the psu that is making this noise. Also if i lean the tower on its side then the noise stops....very strange. I've tried cleaning out the whole pc and all the fans. Didnt actually open up the psu, as I wasnt confident I should do this. Therefore my question is should/can I open the psu and clean it out. Or are there any other ways I could try to stop this very annoying sound?