My GFX card is down. I need a new one. I'm on a Mac Pro 2008 2.8 ghz Quad core. I'm still running os version 10.5.8. I want to get a apple radeon hd 5770. Am I going to have to upgrade to a newer os? I can only run in safe mode Is it possible to update the os in safe mode, or any other way to get a 5770 running with only being able to run in safe mode. thanks.