High Quality Content by WIKIPEDIA articles! U3 was a joint venture between SanDisk and M-Systems , producing a proprietary method of launching Windows applications from special USB flash drives. Flash drives adhering to the U3 specification are termed "U3 smart drives". U3 smart drives come preinstalled with the U3 Launchpad, which looks similar to the Windows OS start menu and controls program installation. Applications that comply with U3 specifications are allowed to write files or registry information to the host computer, but they must remove this information when the flash drive is ejected. Customizations and settings are instead stored with the application on the flash drive.