, if your talking about software cd/dvd you want to load i.e antivirus or powerdvd etc, you could copy the complete files from the disc to usb/sd and install from there. some discs do have copy protection i.e secure disc so in some circumstances i.e games it may not work. this also applies if you need the software cd to actually run the software again in that instance dougs solution above is the best way
if you have a serial number you could download a trial version and enter the serial number you have but again a bit hit and miss