hdd will not load

Hi there. I am new to this site, but I have a friends MacBook Pro Unibody (White) with 250gig harddrive. I went to put Lion on it for him and it crashed! I tried to put Snow Leopard back on and I got the STOP symbol and a BLACK screen! He hasn't done a back-up of the drive so restoring doesn't work either....can somebody please let me WHY! I have used the disc utility, when Lions start, as it tells me it can go no further. The drive seems fine as I have done Verify/Repair. Unformatted it and then re-formated it with the partition and it tells me all's well; but when I restart it does exactly the same thing!...HELP PLEASE AT WITS_END!

Thanking you all in-advance for your help.