Hi there, thanks for your suggestion. As I mentioned, I once again striped the mac bare removing all the RAM and PCI cards, but still no boot up. I removed the battery too and held down the CUDA button (15 seconds OK?), put battery back etc. No boot up at all. This was the same whether one stick of RAM or no RAM at all, but interestingly I didn't get any bad ram chimes in either case.
Is resetting the PRAM equivalent to removing the battery completely, or pressing the CUDA switch, or should I still do the boot up key combo?
Really the only card I haven't removed is the video card. I'm tempted to try that too. Clutching at straws the only theory I had was that the new battery was drained after putting all the ram and PCI cards back in, so I'm considering ordering another one, but I don't think it really works like that.