Okay, my old PowerMac G5 which is now what my dad is using seems to have decided to throw a wobbler. It simply won't start up, it either doesn't display anything at all, or gets to the grey apple logo and apparently freezes. Now, I've run through all the usual stuff, but it won't start up from any CD except for the Apple Hardware test. While the test reports everything as a success, the fact that it is the only disk that the computer will start up from is suspiciously similar to what happened to my MacPro a little while ago when its graphics card stopped working properly, because as I understand it the hardware test skips the GPU part and just draws directly to the monitor using the graphics card's monitor connector. However, unlike with my MacPro which was obviously still working away quite happily despite its lack of ability to draw to a screen, the G5 doesn't appear to be making any hard drive noise indicating start up. This has me suspicious that it may be a more serious problem like the power supply, which would make sense if it were running the GPU that is the problem if doing so causes the power to step up but it isn't getting enough. I'm not sure what the power drain is like for two hard drives though, but if the GPU is drawing too much it's possible the hard drives just can't get any power either. I've reset the PMU with no luck there, can't seem to get far enough to reset PRAM, and that's all I know to try for a power supply issue. Now, I'm in the difficult position that I've run out of things to try to confirm where the problem lies. I'd like to exhaust all things I can test for myself before I take it in for repair, but I don't have any other machines with AGP graphics cards that I could try, at least I don't think I do; I have a blue & white G3 with ATI RAGE 16mb, is the graphics card removable on that, would it work in the G5? I don't really want to go digging it out from whatever corner its disappeared to if it's going to be a dead end! So, don't suppose anyone has any other ideas of things to try?