Hi!

Here is a partial answer to my own question above: "My Zip drive appears fine when I go to start/computer but not Zip cartridges." Wants to format!
Don't do that because then will not read on the XP.
THIS I RESOLVED MY STARTING THE COMPUTER, THEN ONLY AFTER STARTING THE ZIP & INSERTING A CARTRIDGE - IT WORKS EVERYTIME.

The other problem with the removable HD for USB will still not display on start/computer, but works fine on my XP desktop. It displays in "Device Manager/Disk drives" (USB Device) as working fine + drivers are up to date, but there is no Icon to read it or even reformat under "Start/Computer in Vista" You can hear the the "ping" when you connect HD in the USB.