Ah, if only it were that simple.
Many moons ago the games industry came up with a wonderful invention called "copy protection". The idea of this wonderous innovation was to stop people copying games and playing them without stumping up large amounts of cash to buy some development manager another Audi TT.
Anyhoo ... this copy protection is a clever little beast, it knows when you're trying to fool it and it doesnt like it

It disables your virtual drive so that the image doesnt work, making you buy a proper dvd (remember the Audio TT's?)
But, all is not lost. People like
this can help. They can give you a nifty little file called a "no-cd crack" Like the wood stain, it does exactly what it says on the tin. But, unlike the wood stain, it is simple to use and mess free (almost!). If you cant find your game there, then you cant play it without the dvd ... simple