Patrick, By clean install, do you mean erase the volume that I had done the installation on? I have my drive partitioned into 4 volumes (I know I don't need to, but I prefer it that way). I have 9.2.2 on one volume, and can boot from that with no problem. I had put 10.2.8 on another volume/partition, and could boot from that also, which is why I can't see disconnecting my other 2 drives to try and get it to boot into 10.4 now - I'm not saying that might not work, as Harry suggested, but I'd hate to have to keep disconnecting drives just to boot into a particular one. I've tried reinstalling once with no luck, I repaired the drive with disk utility, though it didn't need it. Now, if I have to erase the volume (and can I erase the one volume, without having to erase the whole disk? Or am I confusing volumes and partitions?) I will, to do a clean install. There was one thing that I hadn't paid attention to in the readme stuff - I did have an external FW drive and my USB printer on board - could that have caused a problem with the install? I think someone may have mentioned this potential. Would that mean my USB hub also? Please say no, though if I *have* to unplug it I will... margaret