Reader X runs in a sandboxed environment. Adobe created this version of
reader to try and reduce the exposure to the OS when reading PDFs,
possibly circumventing exploitation via specially crafted files.
ISC is recommending Windows users update to Reader X to better protect
themselves (http://isc.sans.edu/diary.html?storyid=9976&rss). I
recommend that schools look into Reader X and determine if it can fit
into their Windows builds. If so, the update may save users from
damaging their systems by reading malicious PDFs.