macbook pro question mark in center of screen????

hello all! recently my macbook pro displayed a question mark in the middle of the screen upon start up. after doing a little research i concluded it was the hard drive. since the hard drive was not too expensive, i purchased and installed. upon start up, i'm prompted to install os x snow leopard. however, it will not allow the install? any ideas? could it be something else? thanks for all of your help!

G'day and welcome to the surgeon.

Tell us about the Snow Leopard disc. Did it come with the MBP when new? If so maybe the disc is dirty or scratched, or the optical drive has failed. Blow the optical drive out with compressed air.

Yes, original disc and looks very clean. I'll try blowing out drive. Thanks!