In the good old days, Microsoft would have called it "Microsoft Address Book", waited a few years, then started suing people for using the term "Address Book". More recently, they'd have called it "My Address Book" and then changed it back to "Address Book" in Vista, breaking applications that expected to find "My Address Book". And the 32-bit version would be in "Program Files x86" because it's really important to segregate applications by their bitness.