SOFTWARE COLOSSUS Microsoft is poised to invest $1bn for a 15% slice of Comcast Corporation, the fourth largest cable TV operator in the US. Comcast also owns the QVC home shopping TV network which launched in Britain in October 1993 in a joint 80/20 venture with Sky Television. Microsoft’s interest, however, is unlikely to be in home shopping. The real lure is Comcast’s cable distribution channels which reach 4.3 million US homes, offering the canny Gates a bridgehead in digital TV and secure interactive transactions over the Internet.