Trouble shooting a dual 1.8 G5, no known history - received w/out hard drive or ram. Installed known good ram and ATI video card. Video tests typically fail (1 out of 8 tests pass) in Apple Hardware and Apple Service discs. Fail means the machine locks and needs to be powered off. Replaced video card w/known good Nvidia card, system boots but displays no video. All other tests in Apple Hardware and Apple Service pass. I'm not certain where to go next . . .