How to prevent Finder windows from automatically popping up when I attach a disk?

Question

I have a removable Firewire drive. It has several partitions, many of which have Mac OS installers on them (I'm a developer/sysadmin, and need to reinstall fairly frequently). However, I also use this disk for backup and storage, so I don't want to install an operating system every time I attach it.

Whenever I attach the drive, Finder pops up a couple windows automatically, offering to install the operating system. I'd prefer that Finder not pop up these windows.

Why do only some of the partitions pop up windows? How can I disable it altogether?