well, but i see ure using the only ac extreme gpu cooler in malaysia right?    well this is just my 2 cents, i never really seen a real ac extreme yet.
but i would guess the fan on it must be pwn fan, unless it has on board pwn control, then that would make things more easier.

for pwn fan, there should be 4 wires, black, yellow (or red), green, blue.

black = ground
yellow = 12v, red = 5v; (but i guess its 12v for all fans lah)
green = sense (rpm reading)
blue = control (pwm control)

so if u want constant speed i guess you;ll just have to connect only the yellow and the black to the 12v and ground of your psu cable. well. i only tried that out on normal pwm fan. im not sure how ac extreme fans are like.

(btw from my knowledge of pwm control, i think there should be a value on the control voltage so that the modulation could produce maximum duty cycle. but after googling around it seems like direct connection of the 12V and the Ground to the fan would make it run full speed)

on the other hand, if the fan is controlled by the on board pwm control, then there should be just 2 wires on the fan only. either it should be black or red/yellow.
the black wire should always be ground, then the other one (red or yellow) should be the vcc of the fan, either 5v or 12v, but i think it should be 12v.

but its just theory of mine (regarding the onboard pwm control). you can go google if you want to be sure.

plus, there are molex converters for fan pins/connectors. im not sure where to get it but you can try asking allngp if he has those kind of converters or not.

hope it helps, gluck.

pps; i could be wrong altogether, again, i never knew the schemetics of the fan of an ac extreme cooler.