Metal Gear Solid.What's wrong??

I have today got from my friend, two C.D's of Metal Gear Solid.I have installed the 1st C.D, & tried to play with the 2nd one, which is called as "V.R.Missions".No matter, what C.D I try to play with the following message is displayed " Please insert the correct C.D.Rom,select O.K,restart application.".
What can be wrong with such an old game?Pls help.