HD 5770 Crashing during boot up and post

Hey, I have a HD 5770 XFX. The card crashes during boot up, i.e wavey lines across the screen or no display , with constant rebooting eventually I can make into windows. The card will run fine once in windows i.e games, benchmarks etc, only when I power down the PC again will it not start up again during boot. Does anyone have any suggestions to make the card stable during boot up? I don't have a warranty with the card as I bought it used. I really want to get it fixed any suggestions will be appreciated :)

Quick question to start with, have you got the latest driver for your graphics card?

I am assuming this is a card you purchased and placed in your PC rather than having it arrive with it installed. I would probably shut everything down and check to see that there are no portions of the card touching another card or where it should not touch and it might be good to remove the card, check the slot and make sure that nothing is impeding a good solid connection then reinsert it ensuring both connections from your power supply are fitted correctly in their sockets.

Start the PC in SAFE Mode and see if this changes the boot issue, if it runs fine then I suggest doing a clean installation of the card, i.e. remove the drivers, any Catalyst Software you currently have installed and shut down the PC. From a cold boot see if the problem reoccurs and if not proceed with a brand new instance of Catalyst Software and driver download, it is possible the original you used either had a hiccup loading or was damaged in some manner. If after doing all this the problem reoccurs I would contact XFX Support since the card is under warranty and you have done at this point just about everything save try it in another PC, best of luck.

Im using an antec nine hundred case cooling is def not an issue, when card is in windows gpuz reports 46c at idle and 70c max running furmark etc. I have a 900watt psu, the card is plugged in. The card will boot into windows and runs fine drivers are not the issue as the problems are within booting my pc, i.e at bios level post before windows is loaded. The card must have a physical fault? I have tried using differnet bios's and changing voltages but the card will either boot or not. Could it have faulty memory or maybe the power regulators in the card are faulty? Does anybody have an skills in taking these things apart? Im wandering whether I should take of the fan and see if there is anything weird going on uderneath?