The 3pin models work on a 4pin connector without problems. One of the pins simply remains seen on the outside of the plug for the other models there. The walls for the plug are made thin to allow for this.
What cpu are you running there? The complete copper model not aluminum/copper one you are running works on Socket 775 as well as on AMD 754/939/AM2 boards.
http://www.newegg.com/Product/Produc...82E16835118019