Intel Corp, General Instrument Corp and Microsoft Corp are preparing to announce, any day now, a joint venture to develop a personal computer that will sit atop a cable television set to provide access to and control of interactive services offered via cable, the New York Times reports. As well as up to 500 cable channels, the box would give access to extensive home shopping services and an array of databases. Intel will supply the 80386 microprocessor, Microsoft will do a version of Windows for the new box, which will be designed by General Instrument. Microsoft also says it is near agreements with office equipment manufacturers to create intelligent phones, copiers and facsimile machines that can be controlled by a Windows-based grapical interface.