Inno Setup: Disable components page on upgrade

To hide a page from user use the ShouldSkipPage event method. If you return True in this method, the page won't be shown to user. If False, the page will be displayed as usually. Here 's an example of how to check if the installation is an upgrade and if so, skip the Select Components wizard page:

[Setup]
AppId=B75E4823-1BC9-4AC6-A645-94027A16F5A5
AppName=My Program
AppVersion=1.5
DefaultDirName={pf}\My Program

; here is the place for your [Components] section and the rest of your script

[Code]
const
  UninstallKey = 'Software\Microsoft\Windows\CurrentVersion\Uninstall\{#SetupSetting("AppId")}_is1';

function IsUpgrade: Boolean;
var
  Value: string;
begin
  Result := (RegQueryStringValue(HKLM, UninstallKey, 'UninstallString', Value) or
    RegQueryStringValue(HKCU, UninstallKey, 'UninstallString', Value)) and (Value <> '');
end;

function ShouldSkipPage(PageID: Integer): Boolean;
begin
  Result := (PageID = wpSelectComponents) and IsUpgrade;
end;

---

Another option you mentioned might be to disable all the controls of the page. The next script shows as the previous one how to check if the installation is an upgrade and if so, disables all the controls on the Select Components wizard page:

[Setup]
AppId=B75E4823-1BC9-4AC6-A645-94027A16F5A5
AppName=My Program
AppVersion=1.5
DefaultDirName={pf}\My Program

; here is the place for your [Components] section and the rest of your script

[Code]
const
  UninstallKey = 'Software\Microsoft\Windows\CurrentVersion\Uninstall\{#SetupSetting("AppId")}_is1';

function IsUpgrade: Boolean;
var
  Value: string;
begin
  Result := (RegQueryStringValue(HKLM, UninstallKey, 'UninstallString', Value) or
    RegQueryStringValue(HKCU, UninstallKey, 'UninstallString', Value)) and (Value <> '');
end;

procedure DisablePageControls(Page: TNewNotebookPage);
var
  I: Integer;
begin
  Page.Enabled := False;
  for I := 0 to Page.ControlCount - 1 do
    Page.Controls[I].Enabled := False;
end;

procedure InitializeWizard;
begin
  if IsUpgrade then
    DisablePageControls(WizardForm.SelectComponentsPage);
end;