gta vice city

[sturach]

I've got gta vice city to boot up using gran turismo 3
but the game stops very soon into it and a message come up saying "unable to read disc"
I've tried another copy but this does the same any ideas

is the original game only for booting up the copy ?
e.g once the game is booted up it will play ok?

Why do you need a original disc to be of the same size or greater than the copy ?