I bought a SanDisk Cruzer Micro 2GB Flash drive last week and was dismayed when plugging it in to my Powerbook. Not only was the Flash drive mounted as a new disk in OS X, but a CD drive called "U3" was also mounted. The U3 drive consisted of Windows only software called LaunchPad that installs the U3 system on a Windows computer. The U3 platform allows users to take their applications and data with them on the road. Through the U3 system and a U3-enabled Flash drive you can store applications and run them without the need for a computer. However, this technology does not currently work on OS X. Furthermore, to correctly eject a U3-enabled Flash drive on OS X you have to eject the U3 CD in addition to the Flash drive itself. To make matters worse, the U3 CD does not always show as a mounted CD in the Finder. In all my test I had to launch OS X's built-in Disk Utility, and eject the U3 CD from there. It's a major pain to say the least so I began trying ditch the U3 system on the Flash drive.
After many attempts at formatting the Cruzer I was not able to get rid of the U3 partition using OS X. However, using the U3 software itself on a Windows computer, you can run a U3 uninstaller that will effectively get rid of the read-only partition for you. This turns a U3-enabled Flash drive into a regular Flash drive eliminating all the headaches when using it with a Mac. It's a bit of pain to have to use a Windows box in order to get your Flash drive functioning like you want with OS X, but it's certainly worth the effort. So, for now, either stay away from U3-enabled Flash drives (which are clearly marked as such on the packaging) or find a friend with a Windows box, plugin the Flash drive, access the U3 software, and run the uninstaller.