What is the 1603 Install Error
The 1603 MSI installer error is a generic error code “A fatal error occurred during installation” on Windows 7, Windows 8 or Windows 10. Basically, it’s not specific; anything could have gone wrong.
Microsoft document this error and lots of possible ways to solve it here…
You receive an “error 1603: A fatal error occurred during installation” error message when you try to install a Windows Installer package
Fix AutoCAD specific 1603 Errors
Aside from the Microsoft documented 1603 errors above, AutoCAD itself has numerous issues with their installer mechanism which when failures occur can also generate the generic 1603 MSI error code.
AutoCAD 2020 Licensing Error 1603
It seems that AutoCAD 2020 has some issues installing mainly due to their Licensing system component.
Installation incomplete. Some products failed to install.
AutoCAD 2020 did not install (error code: 1603)
Autodesk documents how to fix it here
All other AutoCAD 1603 Errors
There is an App built which specifically scans AutoCAD’s setup so that either the 1603 error is gone (fixed) or it does not affect the install… Check out the blogs on how to fix your AutoCAD’s 1603 error (if your version is not listed below use the search box at the top right of this page)