Installer should have digital signature
The installer and uninstaller should have a digital signature, to avoid a security warning from Windows.
Ask Inno to sign uninstaller. See Inno Documentation [Setup] SignedUninstaller
A tool to sign the installers, like signcode or signtool http://www.google.dk/search?q=signcode.exe
A signature, for example a self-signed certificate. http://www.google.dk/search?q=makecert.exe