And I have no idea what you want us to tell you?
Writing the type of code that can control a fan is not going to be EASY. You need LOTS of experience and some hardware knowledge.
I'm sorry that you obviously have several new and/or small computers that do not have a parallel port. Unfortunately, that makes the task harder to solve.
Joint Technology (HK) Limited - Usb Series
(That was the first link mathcing "usb to i2c" in google).
And then find a I2C compatible fan controller capable of doing PWM on 12V.