TechTool Deluxe versions 2.5.3 and later work with Mac OS Extended (HFS Plus) format Volumes on which Mac OS X is installed.
You receive TechTool Deluxe if you purchase the AppleCare Protection Plan. TechTool Deluxe versions 2.5.3 and later work with Mac OS Extended (HFS Plus) format volumes on which Mac OS X is installed. TechTool Deluxe is not compatible with volumes formatted in the UNIX File System (UFS).
If you are using TechTool Deluxe version 3.0 or later, you must start up the computer using Mac OS X. If you are using TechTool Deluxe version 2.5.3 through 2.5.7, you must start up the computer using Mac OS 9 to get accurate results.
Important: TechTool Deluxe versions 2.5.3 through 2.5.7 may indicate issues that do not actually exist when the computer is started up from Mac OS X, when you use them in Classic mode. Start up the computer from Mac OS 9 before testing with these versions of TechTool Deluxe. You may switch between the operating systems in the Startup Disk pane of System Preferences. When in Mac OS 9, you can make the same selection in the Startup Disk control panel. See technical document 25271: "TechTool Deluxe: False 'Problems' Reported When Used With Mac OS X 10.0" for more information.