more technical difficulties

[darthfox]

So my trusty external hard drive will not, at the moment, work with the new Mac. I know this can be fixed, because ellen_fremedon's computer took it fine, but I get an error that says "the disk you have inserted cannot be run on this computer", and giving me choices like "initialize", which I know better than to select and lose everything on there, which is quite a bit.

What do I need to do to the new computer to make it accept my external HD?

[eta: The answer is apparently "use the other USB port". Who knew?]