Looks like he may be on a PPC Mac. @Thewall, are you running OS X 10.5? What file system is your external hard drive formatted in (FAT32, NTFS, HFS+)? I don't think 10.5 can read NTFS, so that may be the problem. If that's the situation you're in, you'll either have to install some third party software to let you understand NTFS, or else connect the external hard drive to a PC, turn on file sharing, and transfer the files over a network.
So your question is nothing at all to do with photos then, its that you cannot see the external hard disk at all !
Smirk has answered your Q I think, you are on an older release that cannot see NTFS, but perhaps better phrasing of your questions might help you get better advice?
If this is a one off transfer you might as well copy the photos using memory sticks or CD/DVD, unless there are a humungous amount in which case you'll have to install software on teh Mac that lets it read NTFS (assuming you have an old Mac that cannot do ths without needing extra s/w)
You're right; I was incorrect. I had thought there was a PPC restriction but that's not true. So yes, the problem seems to be that the external drive won't mount on his Mac for some reason. @thewall, I still maintain that if you only want to get data off it this one time, it will probably be easiest to connect the drive to a computer that will mount it and then fileshare the documents across. If, however, you want to use the drive with your Mac in an ongoing basis, we'll have to dig into why it isn't recognized by your Mac.