You put in another card and it works but this one doesn't. That means, I'm sorry to say, that your HD 5770 is now dead. It's an old card so it can be expected. The card isn't fixable I'm afraid, it's just dead. If it's an XFX card, take heart. It has that double-lifetime warranty and all you have to do is pay the RMA fee and they'll send you a modern card with equivalent performance. If it's not an XFX card, I'm afraid it's time to go shopping.