How do you 'calibrate' a mouse?

In the old days, part of the ritual of getting a new joystick was to calibrate it - up, down, left and right, I'm sure you remember the drill. Pending a purchase of a joystick for FSX (which I have just added to a Vista 64-bit powered PC), I have been trying the 'mouse as yoke' option, but I find I only have about 25% right aileron and 25% up elevator - which makes canyon flying interesting but ultimately unsatisfying - How do I fix this?!Cheers.