I blew it . I installed a freeware zip utility to Vista64, it is supposed to be compatible, and works very well in XP. In Vista64, it has problems in its file requester and fails to perform an un-zip. During the install, I foolishly allowed it to associate itself with the .zip file extension. Now, even after a full uninstall, files with the .zip extension have no executable associated with them. How to I convince Vista and Windows Explorer to resume handling zip files?