|Might not be a hardware defect. Intentionally clicking keyboards used to be common and even desired. Sometimes that feature could be enabled in cmos/.bios setup, sometimes it was the keyboard itself. There's even software that adds the click:|
Or could it even be an option within Vista? Check the keyboard options in control panel.
Most likely one of the above is the reason for the clicking. But have you tried a different keyboard?
You're not really green until you're soylent green.