Thank you all for helping me with this. I really appreciate all the assistance I received. The input from this group was invaluable.
According to my detective, she testified that this was the first case she's aware of where we had a storage device, but no computer (usually it's the other way around, and we're searching for any related storage devices). And because the case was already four years old when I got it, there was really no way to go back and find any related computers. The main evidence was the external hard drive itself. I basically recreated the hard drive on a poster board using the SIDs (over 3.5 hours through an expert witness), and then connected the defendant to every single folder in my closing argument. I was lucky to have a jury that understood the argument.
So thanks again, all. You guys are great.