Replace hard drive with new OS X Snow Leopard wont load now

iMac Intel 21.5 EMC 2308

I replace a dead hard drive with a Seagate - Barracuda 1TB Internal Serial ATA Hard Drive modle: ST310005N1A1AS-RK

the swap out was easy but now I cant get the Operating system Snow Leopard I've followed the instructions for formatting the HD to the letter. But still it wont load on it get to about 28Min left and just sits there then it says "unable to load OSX please restart and try again" It cost to dam much to get rid of and the shops want a arm and leg just to take a look. It might be a bad DVD not sure. Was wondering if I need to put the cd that came with the HD in first before putting in the DVD for the OS-X this is becoming quit a problem as the only computer I have is at work right now. Any help would be grateful. Thank you