Microsoft is pulling the plug on MSN TV, a service formerly known as WebTV, as Apple ramps up its set-top box efforts. The pioneering service, one of the first to offer Internet access via television sets, will shut down September 30, Microsoft revealed in an e-mail to subscribers and an FAQ posted to its Web site. WebTV, which was founded by Web entrepreneur Steve Perlman in 1996, was acquired by Microsoft for $425 million in 1997. …