If you"re one of about 200 million people using older versions of Windows and you want the latest security enhancements to Internet Explorer, get your credit card ready. Microsoft this week reiterated that it would keep the new version of Microsoft"s IE Web browser available only as part of the recently released Windows XP operating system, Service Pack 2. The upgrade to XP from any previous Windows versions is $99 when ordered from Microsoft. Starting from scratch, the OS costs $199.