It is indeed Vista's fault, the Palm OS install system pretty much won't work at all in Vista. (still waiting for them to release a bug fix) Not sure why your girlfriend's XP laptop wouldn't work, though - I'd suggest that you reinstall Palm Desktop (Start, Settings, Control Panel, Add or Remove Programs, uninstall it, then reinstall using the CD that came with the Zire or the downloadable installer from Palm's website), hard reset the Zire (stick a paperclip in the reset hole in the back while holding down the power button, wiping its memory), and then try again.
A USB card reader would also work, though the install procedure is considerably more difficult in those cases - you have to manually copy some of the data files from the memory card to your Zire's internal memory, which requires the use of a third-party program like FileZ (
http://www.nosleep.net). But send us an e-mail if the Palm Desktop reinstall doesn't work and we can send you detailed instructions for a card reader install.