If you look at the Fans there 2 holes on one corner Correct Top and Bottom ...
So through the Middle of the fan use your M4x10 mm Bolt through there
And use your self tapper throught the top of the fan to go through the case
Hope that helped
is M4 the type of screw I need? because I found this: http://cgi.ebay.co.uk/M4-HANDLE-SCRE...item6b1aca10bf
the screws I have that almost fit are 30mm long, so if I get 35mm long ones then I should be good right?