A Mac is not out of the question, but still somewhat unlikely. I'll be doing some more reading and research. My XP has been ridiculously stable - I never have to reboot, I've had like one virus scare on this machine (no IE for me, and no Outlook), and it turned out to be nothing, and that seems to be the most usual argument for a Mac. Even my Service pack 2 problems turned out to be a bad RAM problem. Jury's still out!
Many thanks for everyone who had helpful thoughts to share on my new computer advice request!
Now, I've got a stack of orders to label and more to make!