Addit! Pro For Prepar3D
Immediately after running SETUP.EXE I get the error "Failure Writing to the System Registry. The registry may be corrupt, or you may not have the required permissions to write to the registry."
This error is caused by a design limitation of Windows 95. According to Microsoft, keys in the Windows registry can hold at most 64 KB worth of information. If the limit is exceeded, you get the error "Failure Writing to the System Registry. The registry may be corrupt, or you may not have the required permissions to write to the registry". Of course, it's possible you really don't have the correct permissions to write to the registry (this is more likely if you have Windows NT).
Which part of the registry is overloaded with information? Probably "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\SharedDLLs". Setup programs that install components like DLL files make an entry in the SharedDLLs key. Over time, after installing a lot of software, it's possible to exceed the 64 KB limit on this key.
What can be done? Microsoft recommends using Add/Remove Programs to remove software you no longer use. This frees up more room in the registry for new software. See PRB: "Failure Writing to the System Registry" Error Message (http://support.microsoft.com/support/kb/articles/q186/8/97.asp) for more information.
Also, you can install and run RegClean to clean and repair the registry. See INFO: RegClean 4.1a Description and General Issues (http://support.microsoft.com/support/kb/articles/Q147/7/69.asp) for more information.
After performing these steps, reboot your PC then reinstall Addit! Pro.