Note all this is applicable to Windows based computers.

Virtual CloneDrive (source: www.virtual.cd)
To virtualize your library of CDs, you’ll need a program like ImgBurn (the official ImgBurn site is at http://www.imgburn.com/ if you wish to learn additional details about it) to convert your CDs into ISO images.
After you convert your library of CDs into ISO images, you’ll need a program to virtually load or mount them. For this a program like Virtual CloneDrive will do the job.