http://www.microsoft.com/en-us/download/details.aspx?id=38780
Kinda neat though I haven't done much with it yet -- will add more info sometime later when I get a chance to use it more. It's essentially a portable app in that you manually activate/deactivate the driver without all the usual registry baggage that makes most virtual disc drives always on, where they can unfortunately cause all sorts of problems, at least in my experience. The driver says XP but the page says it'll work on Vista & 7 - it also is called a Virtual CD Drive, but the original purpose was to allow Windows installs from an ISO, & win7 used a DVD AFAIK.