OK. I almost always read the "won't start" or "won't install" threads, but I've never seen anything like what's happening to me. Mac Pro 1,1. Upgraded to 8 cores. Apple-branded 5770. 14 gb RAM. Never any problems but minor ones. I did a lot of work on it. This was my Hilo (HI) machine and I last used it May 2012. When I left it, I pulled the AC power, pulled the disks out and stored them safely away. There it sat for nearly 18 months. When I moved permanently here from upstate NY (MP 5,1 in hand) I intended to sell the 1,1. But it wouldn't start. Reset PRAM (several times) and SMC (a couple of times). I though the disk was perhaps bad, and I was going to do a clean Lion install anyway. Found a Lion DVD. Oops, how to open the disk tray? Found another disk with Snow Leopard and Vista on it. Started SL, which after a very long time did come up. Opened optical drive, put in Lion, shut down. Reboot holding Option, there's the DVD, but after some activity, nothing happened for a long time. OK, back to SL, used Disk Utility to initialize the old system disk. Tried again. Nope. OK, what about Vista? Vista started up. More slowly than it should have but it came up and was happy. So I made a USB installation kit for Lion, and tested it on a Macbook . . . yeah, it booted up and brought me to the install screen. So it worked. But it would never work in the 1,1. Take out memory, get down to the original set of sticks before I upgraded. Contact cleaner. Nothing. Move the disks around, nothing. Try to install over the SL installation, nothing. Initialize a new disk on the 5,1 pop it in, try both from DVD and USB, nothing. Let's try Vista again. Yes, the machine boots properly into Vista. So . . . who's got an idea? What possible hardware problem would let Bootcamp work properly (but, I think, slowly on the boot) but not let a Lion installer get rolling? Sometimes the USB starts the job (it has an activity light so I know) and sometimes it doesn't. Sometimes it works properly in a front slot, and sometimes it doesn't. Sometimes there's a lag of several minutes (after I select it in the Options screen) before it starts working. I have more disks I can try, but I don't think that's the problem. Summary: DVD install won't work, USB install won't work, different disks make no difference, and the thing boots happily into Vista.