question mark on boot

I'm getting a screen with a folder and question mark when I start my Macbook Pro. I booted from a Snow Leopard DVD, went to disk utilities and couldn't find my hard drive. I assume my hard drive is fried but I decided to check with the experts in this forum before buying a new one.

If you think my current drive is fried my next question is about replacement drives. I have a mid-2010 Macbook with a 320G hard drive. Can I put in a Seagate 500? My local Best Buy sells them cheap.

Thanks for your help.