Try that HDD on a different system,That'll give you clear idea of what's wrong.If you're ready to get a new psu then go for Corsair CX430V2-2.4k,It's a good solid psu which will run your system well.
Haha, bow theres only one option of buying a new PSU, WHICH I'd planned to buy with a new RAM in December. Looks like the purchase has to be pulled ahead.