QuickBooks Error 1603 is known as one of the notable problems while updating or installing the program. This errors mostly occurs when your Microsoft Operating System has an infected file related to it. This error might come up during the QuickBooks installation process or while you are updating QuickBooks. The error message would look like: Error 1603: The update installer has encountered an internal error. Error 1603: Unable to apply the patch. MSI 1603: Fatal error during installation. Symptoms of QuickBooks Error Code 1603: The company file or database file is locked. The Microsoft .NET 1.1 SP1 or.Net framework 3.5 installers itself are not installed correctly. The Security/Policy/Permissions are not allowing the installation. Windows Temp folder is full. Your entire QuickBooks installation is corrupted. Microsoft Windows installer is corrupted. Your PC frequently crashes with Error 1603 when running the same program. Windows runs sluggishly and responds s