Identifying Inno Setup installers
You can identify an Inno Setup installer by finding the text "Inno" within the installation.exe
 Common Switches
install.exe /sp- /silent /norestart should suit most situations.
NB: the /verysilent switch allows automatic reboot after installation. If you are going to use /verysilent, make sure to use /norestart as well!
You can use the following switches / flags (cited from InnoSetup documentation) to customize your installation:
 /SILENT, /VERYSILENT
Instructs Setup to be silent or very silent. When Setup is silent the wizard and the background window are not displayed but the installation progress window is. When a setup is very silent this installation progress window is not displayed. Everything else is normal so for example error messages during installation are displayed and the startup prompt is (if you haven't disabled it with DisableStartupPrompt or the '/SP-' command line option explained above)
If a restart is necessary and the '/NORESTART' command isn't used (see below) and Setup is silent, it will display a Reboot now? message box. If it's very silent it will reboot without asking.
Causes Setup to create a log file in the user's TEMP directory detailing file installation actions taken during the installation process. This can be a helpful debugging aid. For example, if you suspect a file isn't being replaced when you believe it should be (or vice versa), the log file will tell you if the file was really skipped, and why.
The log file is created with a unique name based on the current date. (It will not overwrite or append to existing files.) Currently, it is not possible to customize the filename. The information contained in the log file is technical in nature and therefore not intended to be understandable by end users. Nor is it designed to be machine-parseable; the format of the file is subject to change without notice.
Instructs Setup not to reboot even if it's necessary.
Tells Setup to exit with the given code instead of 0 if a reboot is required and '/NORESTART' was specified. E.g. '/RESTARTEXITCODE=3010' can be used to imitate the usual Windows Installer exit code to schedule a reboot.
Instructs Setup to load the settings from the specified file after having checked the command line. This file can be prepared using the '/SAVEINF=' command as explained below. Don't forget to use quotes if the filename contains spaces.
Instructs Setup to save installation settings to the specified file. Don't forget to use quotes if the filename contains spaces.
Overrides the default directory name displayed on the Select Destination Location wizard page. A fully qualified pathname must be specified.
Instructs Setup to initially check the Don't create any icons check box on the Select Start Menu Folder wizard page.