If you're experiencing a QuickBooks update getting stuck at 26% and the solution was to temporarily disable Windows Defender, it means that your antivirus software (Windows Defender in this case) was likely interfering with the update process, preventing QuickBooks from writing necessary information to your system registry, which is where settings and data are stored on your computer. 

Explanation:

• Registry Access:

  When QuickBooks updates, it needs to modify certain values within the Windows registry to install new components and configurations. 

• Antivirus Interference:

  Sometimes, antivirus software like Windows Defender can mistakenly identify these registry writes as suspicious activity, blocking the update process and causing it to stall. 

Why Disabling Windows Defender Helped:

• Freeing Up Access: By temporarily disabling Windows Defender, you essentially gave QuickBooks unrestricted access to the registry, allowing it to complete the necessary updates without interruption. 

Important Considerations:

• Re-enable Defender:

  After the QuickBooks update finishes, always re-enable Windows Defender to maintain your system security.

• Check Defender Settings:

  You might also be able to resolve the issue by adjusting Windows Defender settings to allow QuickBooks updates through.

• Other Antivirus Solutions:

  If you use a different antivirus program, the same principle applies - temporarily disabling it might be necessary to troubleshoot QuickBooks update issues.