A: Error 80000003 immediately after launching the installer is usually caused by running Installer version 44.10 on a 68000 or 68010 CPU. Installer 44.10 requires a 68020 or higher CPU.
The issue can usually be solved by replacing the 44.10 Installer software with Installer version 43.3. This is just one file named "Installer", which by default is inside the Utilities directory of the system drive. To be viewed from the Workbench desktop environment, it requires "Window/Show All Files" to be selected, as it does not have an accompanying Amiga icon file.
Both versions of the Installer software are included in the Storage disk of the Classic Support Workbench 3.1 disk set. The Workbench 3.1 installation script performs a CPU check and installs version 43.3 (from the "Update" directory) on systems with a 68000 or 68010 CPU or version 44.10 (from the "Update-68020" directory) on systems with a 68020 or higher CPU. However, if the destination media (e.g. a CompactFlash card) is then used on a system with a lower CPU, it may be necessary to manually "downgrade" the Installer software.