I've succeeded in installing Portable Mail and Address Book to an external Firewire drive, but the Portable iCal installation to the same drive fails. I've tried this with the Portable iCal nested a layer or two down on the external drive, and with it at the top level. The software has reported success on each try, but in each case it turns out that the calendar that's actually displayed is the same one that opens if (non-Portable) Mail is opened. When the portable drive is moved to another machine and Portable iCal is opened, the calendar that appears is whatever is resident on that machine. Any suggestions?

Sorry I've to test it on 10.5 but I've not it available yet.