Theres only 2 differant threads used in a case, theres the 6-32 and the M3 I think it is. you can get them at most hardware stores. M3 is used on CD/DVD drives and some motherboard standoffs, 6-32 is used about everywhere else and also some MB standoffs. Fans on the other hand use something tottally differant, I believe there #8 screws but they are special fans screws but i seen people use sheet metal screws before.