Microsoft Virtual CD-ROM Control Panel
Once mounted, your virtual CD/DVD will be available under Windows as a normal drive letter so you can browse and copy files, or run programs from it just as if you had a regular CD in your optical drive. However, just as with a normal CD/DVD-ROM disc, you can't write files to it. If you're looking for something persistent, i.e. remounts image automatically when you boot, then look to the aforementioned Daemon Tools. If you want something quick and dirty that doesn't require installation then Virtual CD-ROM Control Panel fits the bill perfectly--I keep a copy on my emergency thumb drive.
Note: Note: The only documentation that accompanies the program is a short readme which indicates that you must install the VCdRom.sys in the system32\drivers folder. This seems to be mistaken. I've been able to load it consistently from the same directory that I keep the program in on a thumb drive. This link takes you to the vendor's site, where you can download the latest version of the software.
--Jon L. Jacobi