On closing the Add-In Manager, Microsoft Excel 95 would normally attempt to add an "Open=" line to the registry so that installed add-ins will be loaded at startup. Microsoft Excel also looks at the InitCommands and InitMenu registry key values to find additional add-ins that need an "Open=" line.
You should not name an add-in with an underscore in Microsoft Excel 97 because it makes an exception to those registry key values beginning with '_'. It ignores those registry key values and does not automatically add an "Open=" line for them. Add-ins that install a InitCommand or InitMenu registry key value with a '_' prefix will not be opened at startup.