Being something less than technologically savvy, it took me a while to figure this out, too. Here's what I did:
1) Install MOO2 normally.
2) Nose around in Program Files until I found where they all went.
3) Copy everything from the CD into that same spot. Been a while now, but I think I just "selected all" on the CD and dragged and dropped the files.
4) Find the appropriate file (I think it's "orioncd.ini.")
5) Back up the file you're about to change.
5) Copy and paste the "new" directory for your stuff over the "old" one.