Hello. I have installed BirdieSync 1.6.x.x on my old OS (Win2000) and bought the registration-key. It has worked 100% with T-Bird and ActivSync 4.5............. Since 3 month I use a new OS (Vista Home premium) and have installed BirdieSync 1.7.0.4, because Version 1.6.x.x doesn't work with Vista ...