The Install option is controlled by a inffile File TYPE entry in the Classes key at HKEY_LOCAL_MACHINE\Software\Classes\inffile

Here is a Save Subtree As:

                              Key Name:          SOFTWARE\Classes\inffile\shell                              Class Name:        <NO CLASS>                                                             Key Name:          SOFTWARE\Classes\inffile\shell\Install                              Class Name:        <NO CLASS>                                Name:            <NO NAME>                                Type:            REG_SZ                                Data:            &Install                                                             Key Name:          SOFTWARE\Classes\inffile\shell\Install\command                              Class Name:        <NO CLASS>                                Name:            <NO NAME>                                Type:            REG_EXPAND_SZ                                Data:            %SystemRoot%\System32\rundll32.exe setupapi,InstallHinfSection DefaultInstall 132 %1