Hi - I hope someone out there might be able to help. I've searched the web and this website and can't find a solution to my issue...details below. I have two Macs both of which are running snow Leopard. To back these up I use time machine connected to a single external USB hard drive. I simply connect the drive to the machine I want to backup once a week or so and it will back up. For a while, everything worked just fine, I even needed to recover files from it and did so successfully. Occasionally one or other of the Macs would take a while to recognise the drive but normally it would be OK. Gradually the problem got worse until neither machine would recognise the backup drive. I mean nothing - not only would it not mount on either machine but wasn't recognised in disk utility either. As the disk was about 3 years old I figured it was probably the drive on the way out so bought a new Seagate drive to replace it. Again, it worked fine to start with, but now after only about two months exactly the same problem has occurred and now the new drive is not recognised at all either. Now it could be that I'm just unlucky and have two dead hard drives but I don't think so, especially as the new drive has had very little use. I'm guessing that somehow using the backup drive with more than one machine has caused the problem but I don't know how to fix it. I have tried everything my (limited) knowledge will allow. - Repairing disk permissions - Allow OSX time to find the drive (I've left it for hours but to no avail) - Booting the machine up with the usb drive already plugged in As the drives are not recognised by either machine at all, I don't know what else to do. If I could see the drives I'd be happy to format them both and use one on each machine if this would fix the problem but I can't even do that. Does anyone have any suggestions or can shed some light on this? Thanks in advance. Dom.