iMac won't startup after new OS download

[bballhoop]

Hello all,
I know this is an extremely late update, but I was running Leopard for quite some time and I found out I had to purchase Snow Leopard if I wanted to get Mountain Lion, or better yet be able to update to Mavericks once it releases. So I loaded the new OS (ordered straight from Apple) and as soon as the computer rebooted, it froze on startup. The apple logo appears along with the spinning wheel but then it freezes on a completely grey/white screen or light blue screen.
I have gotten to the desk top 2 or 3 times when this first happened, but it just froze after a few seconds. Now it will not get there.
I have tried:
Reset nvram
Safe boot (bar comes up under apple logo and loads near the end but freezes)
Single user mode - did fsck and it found a problem, then rebooted and still froze
Can't get it to do the apple hardware test.
Won't startup holding the C key.

This is an intel based iMac, from 08 or 09. What do you all suggest I try? My computer worked great and now it is completely useless..
I'm not worried about what I have on the computer, I would be completely fine if I could just wipe everything and start from scratch if it meant I could use the computer again.

 

[Saltymac]

Did you save a copy of your previous working system on another drive ? If so start from it and get to your desktop. This will rule out a new (ghost) hardware problem. Use sys pref to see if your new installation shows as a bootable one. If yes try to boot from the disc. If it won't start or doesn't show up I would repartition disk and reinstall Snow L.