Most of games and software's in these days require to having the CD to run it or to repair and modify its contents. For the people who download or copied bunch of setup files on to their computer this is going to be a nightmare.
There is lot of Disk image standards. So the tool you are trying to use must have the ability to open that image type. For an example standard ISO image files can be open from lot of programs. Like Alcohol, Daemon tools, Nero image drive........... etc.
In here i'm attaching a link to download a free powerful tool that you can use to open disc images. It's called Magic Disc .
After installing it you'll notice that another CD / DVD Rom is appearing on your computer. In this program you'll get a system tray icon too.
You can right click on that icon in the tray area and select virtual CD/DVD-Rom
Select one of the virtual CD/DVD Roms and select Mount
Browse and select the disk image you wish to mount then press ok.
Need more help on mounting CD images ?