I think your first course of action would be to return the hard drive and try again. Then if its the same problem then start to look at memory etc. Not sure how much memory you have but its normally in pairs or made up of more than one module, so you could try takling one of the modules out and then trying again, if that didnt work try with another module and so on. A friend had a probelm on his PC and this method of removing memory, effectively testing each module on its own, found the problem memory quickly.