I have been using Virtual CloneDrive to mount .iso files since the MS Virtual CD-ROM Control Panel lost usefulness.
I just stumbled onto WinCDEmu, a sourceforge.net project. They have a portable version as well (installs a driver of course). The portable verision functions similary to the MS Virtual CD-ROM Control Panel, where the driver is installed/uninstalled and .iso files are mounted and unmounted all from a single GUI.
I'm still baffled that with all the other useless garbage that comes with Windows, why the ability to mount an ISO is left out. I'd easily give up the "Math Input Panel" or any of the various wizards for doing <insert name of standard task everybody should already know how to do> in exchange for a native ISO mounter. :)
I've been using MagicISO (as well as Virtual Clone) and never liked that they were such a permanent thing. The fact that this is portable and can be removed is pretty cool. Thanks for sharing!