What Does Windows NT 4.0 Look for in Terms of a Valid Windows NT 3.51 Installation?

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• If an application or the user has altered the Software hive version or Product ID, Windows NT setup will not find a valid upgrade path. If the Software hive is corrupt, the computer typically will not boot.
• If the Software or System hives are corrupt, Windows NT Setup will not find a valid installation and require a clean install. A possible work around is to export third-party registry keys, particularly in the Software hive, until the Software hive is recognized as valid. Then reinstall the 3rd-party components after the upgrade.
  
  NOTE: You can run Rdisk.exe and select update repair information then expand the System._ and Software._ files found in the %SystemRoot%\Repair directory. Using Regedt32 on another Windows NT computer running the newer version, try to load the expanded System or Software Hives to see if they load without error.
• Windows NT will parse the Boot.ini file or look in NVRAM on RISC computers to find a valid Windows NT installation. The Boot.ini entries must be correct and should follow these guidelines:
  • Contain no spaces in the ARC path except: "The description between quotes"
  • Contain only ACSII characters and end with a CR LF - use EDIT.COM to add a hard return after each line
  • Contain no blank lines between entries
• If Windows NT does not find a valid installation, ensure that the boot drive and the system drive are attached to disk controllers that are detected by Windows NT. One drive may be controlled by a retired driver or a controller driver that is not being detected (though in most cases this will result in a STOP: 0x0000007b - inaccessible boot device error message). If the error is occurring, use F6 during the hardware detection phase ("Setup is examining your hardware configuration") to select the correct controllers or load a 3rd party device driver.
  
• Windows NT will not upgrade Server to Workstation. Make certain the system being upgraded is not a member server.
• There is no back-door to fooling setup for upgrade purposes. If the Windows NT 3.51 installation is deleted, you will need a Windows NT 3.51 CD (the "Step-Up" Version will work) to continue.
• In some cases, a parallel installation of Windows NT will help Setup identify the original installation as an upgrade candidate.
• The resource kit utility C2config.exe (C2 Configuration Manager) Registry Security option was run on the Windows NT 3.51 computer before the upgrade. The registries Access Control List entries (permissions) had been changed so that setup was unable to access the information necessary to locate the previous installation. This is by design and is part of the C2 Security specification.