To rebuild the computer's main drive, you must start up the computer from another source. There are many options to do so.

The downloaded software will not start up your computer since it does not include any System files. 

You will need to utilize one of the following configurations to use the legacy DiskWarrior 4.x application (please read carefully as not all of these may be relevant for your configuration):

(1) Alternate Startup Disk

If you have an external drive such as...

FireWire (PowerPC or Intel) USB2 or newer (Intel only) Thunderbolt (Intel only)

(2) Or a secondary internal drive or partition...

You can download and install OS X 10.10 Yosemite (most recent version supported by DiskWarrior 4.4) nn that drive; start up the computer from the operating system on the external/secondary device. Once you have started up the computer from the newly-installed operating system, install DiskWarrior into the “Applications” folder. Then, you can launch DiskWarrior from the Utilities folder of the external/secondary device to rebuild the directory of the computer's main hard drive.

Please review the following link to see how to utilize the downloaded OS X 10.10 Yosemite to install the operating system onto an alternate drive:

https://support.apple.com/en-us/HT210717

(3) Target Disk Mode: Connect two Macs with a FireWire or Thunderbolt cable (not all options will be applicable depending on the model of your computer) where one is the “host” and the other is a “target”. The host Mac should be running OS X (10.5.8 "Leopard" or higher). In this scenario, the target Mac is the computer whose internal hard drive you want to repair. Start by shutting down the target Mac. Then turn it on while holding down the “T” key. The target Mac’s drive will appear as an option via the DiskWarrior interface. Run DiskWarrior from the Applications folder of the host Mac and rebuild the target Mac’s disk.

DiskWarrior 4 version 4.4 is not compatible with OS X 10.11 or later. To restore complete functionality and to gain additional features, please upgrade to DiskWarrior 5.

The previously released DiskWarrior 4 version 4.4 is required to run an installed copy of DiskWarrior while started from 10.10 Yosemite.

If you haven't already done so, you can use the free updater for existing owners of DiskWarrior 4 versions 4.0-4.3.

The previously released DiskWarrior 4 version 4.4 is required to run an installed copy of DiskWarrior while started from 10.9 Mavericks.

If you haven't already done so, you can use the free updater for existing owners of DiskWarrior 4 versions 4.0-4.3.

DiskWarrior 4 version 4.4 was released last year and is required to repair the directory of a Fusion Drive. You must be started from OS X 10.8.2 Mountain Lion, or later, to rebuild the directory of a Fusion Drive.

If you haven't already done so, you can use the free updater for existing owners of DiskWarrior 4 versions 4.0-4.3.

DiskWarrior 4 version 4.4 was released last September and is required to run an installed copy of DiskWarrior while started from 10.8 Mountain Lion.

If you haven't already done so, you can use the free updater for existing owners of DiskWarrior 4 versions 4.0-4.3.

Gatekeeper is a new feature of OS X 10.8 Mountain Lion that helps protect you from downloading and installing malicious software on your Mac. Developers can now digitally "sign" their applications so that they are identified as being produced by a known developer such as Alsoft. If a downloaded application is signed by an identified developer, the default behavior of Gatekeeper is to allow you to use the application. Downloaded applications that are not signed cannot be used with a simple double click.

As of today, all copies of DiskWarrior and the DiskWarrior 4 version 4.4 updater that are downloaded from the Alsoft site are digitally signed. This allows you to run these downloaded applications by simply double clicking as you normally would.

What about older downloaded copies of DiskWarrior? Gatekeeper only checks to see if a downloaded application is okay to run if it has not been run before. So you don't need to do anything with older copies of DiskWarrior that you have installed and run prior to installing OS X 10.8 Mountain Lion. If you install an older downloaded copy of DiskWarrior after installing OS X 10.8 Mountain Lion then you can indicate to Gatekeeper that it's okay to run DiskWarrior by control (or right) clicking on the DiskWarrior application and choosing open from the pop-up menu that appears. You'll only need to control (or right) click the first time you run the older downloaded copy of DiskWarrior.

What about DiskWarrior on a DVD or CD? Applications on DVD are not downloaded and therefore are not checked by Gatekeeper.

DiskWarrior DVD revision 1109 was released containing the new DiskWarrior 4 version 4.4. This DVD is identical to the older DVD revision 1107 that it replaces except that DVD revision 1109 contains the new version of DiskWarrior. All Mac models meeting the system requirements for DiskWarrior 4 can be started from the DVD.

Owners of DiskWarrior 4 versions 4.0-4.3 can now download a free disc update to update to DiskWarrior 4 version 4.4. This free updater application allows you to create a new startup disc (CD/DVD) with the latest version of DiskWarrior using your original DiskWarrior 4.0 to 4.3 disc. This approach provides you with an instant update while maintaining your ability to start up from a disc containing the latest version of DiskWarrior.

The DiskWarrior 4.4 Disc updater cannot update a disc created by any previous DiskWarrior updater. You must update your original (factory) DiskWarrior 4.0 to 4.3 disc. This limitation allows us to reduce the size and complexity of the updater. It also results in a significantly smaller test suite that permits us to issue updates more responsively.

Please note that the new startup disc you create will start up the same set of Mac models as your current DiskWarrior disc (CD/DVD). Your new disc will not start up any Mac that your current DiskWarrior disc can not. If you need a new DiskWarrior disc that can start up the newest Mac models, please contact our Sales Department to order. Please note that you will receive a DVD even if your previous DiskWarrior disc was a CD.

DiskWarrior 4 version 4.4 is now available. This release features ongoing internal enhancements for speed and improved repair.

A free updater for existing owners of DiskWarrior 4 versions 4.0-4.3 is also available for immediate download (see below).

DiskWarrior DVD revision 1107 was released to start up the new MacBook Pros (introduced February 24, 2011) and the new iMacs (introduced May 3, 2011). Some newer iMacs with wireless keyboards have timing issues when starting up from any DVD. Instead of pressing the "C" key immediately upon start up, wait for the startup chime and then press the "Option" key. This will bring up the Startup Manager which will allow you to choose the DVD as a startup disk. If your wireless mouse is not working in the Startup Manager, use the arrow keys to choose the DVD, then press the "Return" key to continue starting up.

DiskWarrior 4 version 4.3 was released in March and is required to run an installed copy of DiskWarrior while started from 10.7 Lion.

If you haven't already done so, you can use the free updater for existing owners of DiskWarrior 4 versions 4.0-4.2.

Owners of DiskWarrior 4 versions 4.0-4.2 can now download a free disc updater to update to DiskWarrior 4 version 4.3. This free updater application allows you to create a new startup disc (CD/DVD) with the latest version of DiskWarrior using your original DiskWarrior 4.0 to 4.2 disc. This approach provides you with an instant update while maintaining your ability to start up from a disc containing the latest version of DiskWarrior.

The DiskWarrior 4.3 Disc updater cannot update a disc created by any previous DiskWarrior updater. You must update your original (factory) DiskWarrior 4.0 to 4.2 disc. This limitation allows us to reduce the size and complexity of the updater. It also results in a significantly smaller test suite that permits us to issue updates more responsively.

Please note that the new startup disc you create will start up the same set of Mac models as your current DiskWarrior disc (CD/DVD). Your new disc will not start up any Mac that your current DiskWarrior disc can not. If you need a new DiskWarrior disc that can start up the newest Mac models, please contact our Sales Department to order. Please note that you will receive a DVD even if your previous DiskWarrior disc was a CD.

DiskWarrior DVD revision 1102 was released to start up the iMac Core i3, i5 and i7 models, the MacBook Pro models (introduced April 13, 2010), the new MacBook Air (introduced October 20, 2010), the new Mac Mini models (introduced June 15, 2010) and the new Mac Pros (introduced July 27, 2010). The MacBook Pro models introduced February 24, 2011 cannot be started from DiskWarrior DVD revision 1102. A new DVD will be released to start up the new MacBook Pros once Apple, Inc. releases new system startup files to Alsoft, Inc. and other developers

DiskWarrior 4 version 4.3 is now available. This release features ongoing internal enhancements for speed and improved repair.

A free updater for existing owners of DiskWarrior 4 versions 4.0-4.2 is also available for immediate download (see below).

DiskWarrior DVD revision 1001 was released to start up the new Mac mini, MacBook and iMac models released in late October. The iMac Quad-Core model is still not supported. The DiskWarrior application is unchanged and remains at version 4.2.

DiskWarrior DVD revision 909 will begin shipping on Tuesday, September 1. The new DVD contains DiskWarrior 4 version 4.2 and adds support for starting up the new 13" and 15" MacBook Pro (SD card slot) models introduced in June 2009.

Owners of DiskWarrior 4 versions 4.0-4.1.1 can now download a free disc updater to update to DiskWarrior 4 version 4.2. This free updater application allows you to create a new startup disc (CD/DVD) with the latest version of DiskWarrior using your original DiskWarrior 4.0 or 4.1 disc. This approach provides you with an instant update while maintaining your ability to start up from a disc containing the latest version of DiskWarrior.

The DiskWarrior 4.2 Disc updater cannot update a disc created by any previous DiskWarrior updater. You must update your original (factory) DiskWarrior 4.0 or 4.1 disc. This limitation allows us to reduce the size and complexity of the updater. It also results in a significantly smaller test suite that permits us to issue updates more responsively.

Please note that the new startup disc you create will start up the same set of Mac models as your current DiskWarrior disc (CD/DVD). Your new disc will not start up any Mac that your current DiskWarrior disc can not. If you need a new DiskWarrior disc that can start up the newest Mac models, please contact our Sales Department to order. Please note that you will receive a DVD even if your previous DiskWarrior disc was a CD.

DiskWarrior 4 version 4.2 is now available for compatibility with Mac OS X 10.6 (Snow Leopard). Among the new features in version 4.2 are enhanced and faster directory repairs. Click here for limitations on using the older DiskWarrior version 4.0 or 4.1 with Snow Leopard.

The new version is available for sale on the Alsoft ecommerce web site. Purchases of new copies from the e-commerce web site result in an immediate download with companion DVD shipments starting in 4 days on Tuesday, September 1 (see next item below). A free updater for existing owners of DiskWarrior 4 versions 4.0-4.1.1 is also available for immediate download (see second item below).

DiskWarrior 4 version 4.1.1 (released 10/27/2008) is compatible with Mac OS X 10.5.8 (Leopard).