3 and 4 pin connectors are compatible with each other, there is a notch that won't let you connect them in wrong way, but then you managed to connect FDD there so...
If you connect 4 pin female (fan) to 3 pin male (mobo), make sure the BLUE
wire remains unconnected.
If you connect 3 pin female to 4 pin male, then do like this:
4th pin is where the blue wire would be, which is used for PWM speed control (in which case you have to control it by voltage adjustments, not every fan header on non-Gigabyte boards can do this!).
I really hope you didn't damage your fan header, or even worse - the motherboard by connecting that FDD there...
First time builders, PLEASE, LOOK THROUGH THE MANUALS BEFORE DOING ANYTHING, 15 minutes now saves you A LOT of trouble later on.Edited by Thewaster - 5/7/11 at 12:52pm