It depends on what you are trying to do and what the disk is.
The previous suggestions will copy the files as they are stored on the disk although if a program disk it may fail if the disks incorporates copy protection.
An alternative is to create an ISO image of the disk contents as a single file. There are others but I use ISORecorder from Alex Fienman to create the image.
This can then be mounted as a virtual disk with its own drive letter.
https://www.microsoft.com/en-us/download/details.aspx?id=38780