Ethan, I am supremely unqualified to give Mac advice. But I know a few Mac users who are able to run Obsession (I) Offline using virtual x86 (i.e. PC) emulation software like Parallels. The key is that you need a DOS (or FreeDOS) installation to install Obession Offline to. Alternatively, I know people who maintain an obsolete PC (..that was discarded by an IT department, and thus free to them) solely to run Obsession Offline (OOL).
You cannot run OOL under WinXP, and you cannot read Obsession I shows with Obsession II Offline. It is possible to install OOL on XP machines by partitioning the hard drive with a tool like Partition Commander, but this is an advanced technique I don't recommend to a Mac user. (That's not meant to sound patronizing, I just mean that if you wanted or needed to be a PC expert, you wouldn't have bought a Mac, and you certainly made the right decision!)
Tim
www.etcconnect.com