Note that this trick will not work for every game, even if the disc is accepted. For example, it works for Morrowind, but not Oblivion. In this example I will be using icewind Dale II.
You must know the basics of how to use a wrapper and its tools (mainly Winecfg)
Just the wrapper and a working DVD drive
You must install your game into the wrapper and have it in a working state. If you are satisfied with the way it runs, we can then proceed.
First, insert your disc and note the name it is given (In my example that would be "ICEWIND2_2").
Open your wrapper's contents, navigate to /Contents/Ressources (the folder containing the "drive_c") and create a folder with that exact name. Copy your disc's entire contents into that folder. Don't worry about file size, we will trim it down later, but for now it's better to be on the save side.
Now, open Winecfg and go to the "drives" tab. Add a new drive below C and enter "../[NAME OF FOLDER]" as the path (without the brackets, in my example that would be "../ICEWIND2_2"). Click "Show Advanced" and set the type to CD-ROM.
That's it basically, eject the disc and try the game out. If everything works fine we can now start trimming the folder's contents until we reduce it to a few Megabytes (or even Kilobytes). Basically, what you have to do is open the folder, delete a bunch of files and see if the game still runs. If it does, delete something else; if it doesn't, put the files back and delete something else. Repeat this process until you are left with only the files needed. In the case of Icewnd Dale II the would be "CD2/Data/IWD2CD.2", reducing the total filesize to merely 12KB. The best stategy is to start with the largest files, such as videos and textures, first.
Now you can enjoy you favourite games more comfortably without the risk of breaking anything. Keep in mind that this will not always work, even when it's the same game or an expansion pack. Baldur's Gate II works fine, but the expansion, Throne of Bhaal, still needs the actual CD. Some game might have re-releases that use stricter copy-protection than older prints. However, it's still worth a shot, since the process is very straight-forward.