I recently had trouble syncing my Android with my PC using Vista, & kept receiving the message that I needed a driver for my phone to accomplish this task. The following is a portion of the email I received from Motorola regarding this issue. As I spent a significant amount of hours on this, I hoped that this might save someone else's time!
If a consumers PC asks them to insert a disk when they plug droid, the drivers were not automatically detected. The official consumer link for Motorola drivers is : http://www.motorola.com/consumers/v/index.jsp?vgnextoid=bda09ec8009a0210VgnVCM1000008806b00aRCRD Version 4.0 support DROID
Best of luck! Tambo