grinding sound please help

[xzxremixxzx]

hello i just build a i7 cpu this past weekend and i noticed the past 2 days everytime i have the computer on for 3 hours or so i get a grinding sound. can someone please help idk what this is

 

[Baez]

You'll have to take the cover off your case when you hear it and see for yourself. It could be any of the fans doing it.