imac won't accept the cd?

hi,

been having this problem basically i put the cd in and it sounds like it's trying to work, makes some weird noises and then spits it out

for a while, at first it was only doing it a bit and eventually it worked, but now it won't accept the cd at all and just goes in, makes a weird noise and then spits it out.

is there anyway to play the game without the cd on the mac? i know there's steam on the PC, but does that work for mac (sorry if i'm being naive here).

Or is there anything you can send me to make it work.. i have all the box, serial codes etc. It's really starting to cheese me off tbh. I don't see why i should have to pay out for a new disc. i've tried other types of cds and it was fine...

thanks.

You can get steam for Mac now