I use Virtual CloneDrive, it's free and easy to use. For more info and download visit developer website here
Installing the software will automatically create Virtual DVD drive. Uninstalling will remove it, easy right?
After installation you can see the new drive by clicking (Windows 7) START and COMPUTER.
On my computer it looks like this:
Virtual drive lingo : Mount = Insert DVD, Unmount = Eject DVD
As an alternative you can use Daemon Tools Lite Get it here , also free but not as easy as Virtual CloneDrive.