External HD

I know there are a couple of techies who sometimes stumble in here, so I have a question:
I am looking for an external HD. I have a library program, Libronix, that is oh, 6 gigs (it contains literally thousands of books in digital format, all searchable, pretty cool), and could expand quite a bit. They let you install it on multiple computers (3, I think), so I got to thinking that I could install the base program on my wife's laptop, then install the library on an external HD so as to not fill her internal HD
So, I need to know if I should go with a USB or Firewire connection, or both. I want to be able to (fairly) quickly search the library when I am in class or on the road somewhere. It doesn't have to be lighting, but 3 hours won't cut it either.
Here is another issue. My desktop does not have USB 2.0 (thank you Lexar) or a Firewire connection, so if I want to transfer anything, is there a Firewire card for PC's, or a way to repair my USB 2.0 bus (I think the Lexar jump drive fried it, but I haven't had the time to look at it, not that I could tell. Suffice that anything I plug into my front USB ports gives me the popup "USB device found.....There is a malfunction with your device, unplug it and try again.")?
Any advice will be received with gladness and thankfulness.

Guess Who!

See if you can figure out who said this:
"And we, too, being called by His will in Christ Jesus, are not justified by ourselves, nor by our own wisdom, or understanding, or godliness, or works which we have wrought in holiness of heart; but by that faith through which, from the beginning, Almighty God has justified all men; to whom be glory for ever and ever. Amen."

Hint: It was written in Rome