How to uninstall a program mistakenly installed in the "Program Files(x86)" folder and install it anew in the 64-bit "Program Files" folder

Question

I am using innoSetup to create a software installer. However, by default, innoSetup installs to "Program Files(x86)", which I have mistakenly distributed to my users.

And many users install the software in the x86 directory using a 64-bit Windows environment.

I created an installer for the new version of the software with innoSetup and designed it to install correctly in "Program Files" for 64-bit.

However, the programs already installed in "Program Files(x86)" are not uninstalled and remain. How can I uninstall them?

A similar question exists in the past on stack overflow, but it did not solve my problem.

I had initially written the following code. This was installed in the "Program Files(x86)" folder, even when used in a Windows 64-bit environment

; Script generated by the Inno Setup Script Wizard.
; SEE THE DOCUMENTATION FOR DETAILS ON CREATING INNO SETUP SCRIPT FILES!

#define MyAppName "testApp"
#define MyAppVersion "1.00"
#define MyAppPublisher "taichi"
#define MyAppURL "https://testApp.com/"
#define MyAppExeName "testApp.exe"

[Setup]
; NOTE: The value of AppId uniquely identifies this application. Do not use the same AppId value in installers for other applications.
; (To generate a new GUID, click Tools | Generate GUID inside the IDE.)
AppId={{xxx-xxxx-xxxxx-xxx}
AppName={#MyAppName}
AppVersion={#MyAppVersion}
;AppVerName={#MyAppName} {#MyAppVersion}
AppPublisher={#MyAppPublisher}
AppPublisherURL={#MyAppURL}
AppSupportURL={#MyAppURL}
AppUpdatesURL={#MyAppURL}
DefaultDirName={autopf}\{#MyAppName}
DisableProgramGroupPage=yes
; Uncomment the following line to run in non administrative install mode (install for current user only.)
;PrivilegesRequired=lowest
OutputDir=C:\Users\taichi\Desktop
OutputBaseFilename=testAppSetup
Compression=lzma
SolidCompression=yes
WizardStyle=modern

[Code]

/////////////////////////////////////////////////////////////////////
function GetUninstallString(): String;
var
  sUnInstPath: String;
  sUnInstallString: String;
begin
  sUnInstPath := ExpandConstant('Software\Microsoft\Windows\CurrentVersion\Uninstall\{#emit SetupSetting("AppId")}_is1');
  sUnInstallString := '';
  if not RegQueryStringValue(HKLM, sUnInstPath, 'UninstallString', sUnInstallString) then
    RegQueryStringValue(HKCU, sUnInstPath, 'UninstallString', sUnInstallString);
  Result := sUnInstallString;
end;

/////////////////////////////////////////////////////////////////////
function IsUpgrade(): Boolean;
begin
  Result := (GetUninstallString() <> '');
end;

/////////////////////////////////////////////////////////////////////
function UnInstallOldVersion(): Integer;
var
  sUnInstallString: String;
  iResultCode: Integer;
begin
// Return Values:
// 1 - uninstall string is empty
// 2 - error executing the UnInstallString
// 3 - successfully executed the UnInstallString

  // default return value
  Result := 0;

  // get the uninstall string of the old app
  sUnInstallString := GetUninstallString();
  if sUnInstallString <> '' then begin
    sUnInstallString := RemoveQuotes(sUnInstallString);
    if Exec(sUnInstallString, '/SILENT /NORESTART /SUPPRESSMSGBOXES','', SW_HIDE, ewWaitUntilTerminated, iResultCode) then
      Result := 3
    else
      Result := 2;
  end else
    Result := 1;
end;

/////////////////////////////////////////////////////////////////////
procedure CurStepChanged(CurStep: TSetupStep);
begin
  if (CurStep=ssInstall) then
  begin
    if (IsUpgrade()) then
    begin
      UnInstallOldVersion();
    end;
  end;
end;

[Languages]
Name: "english"; MessagesFile: "compiler:Default.isl"
[Tasks]
Name: "desktopicon"; Description: "{cm:CreateDesktopIcon}"; GroupDescription: "{cm:AdditionalIcons}"; Flags: unchecked

[Files]
Source: "C:\Users\taichi\Documents\hold\testAppDevelop\dist\testApp\testApp.exe"; DestDir: "{app}"; Flags: ignoreversion
                                                           

[Icons]
Name: "{autoprograms}\{#MyAppName}"; Filename: "{app}\{#MyAppExeName}"
Name: "{autodesktop}\{#MyAppName}"; Filename: "{app}\{#MyAppExeName}"; Tasks: desktopicon

[Run]
Filename: "{app}\{#MyAppExeName}"; Description: "{cm:LaunchProgram,{#StringChange(MyAppName, '&', '&&')}}"; Flags: runasoriginaluser nowait postinstall skipifsilent
                         

After modifying the code as follows, the software was installed in Program Files. However, the files in Program Files(x86) were not uninstalled.

; Script generated by the Inno Setup Script Wizard.
; SEE THE DOCUMENTATION FOR DETAILS ON CREATING INNO SETUP SCRIPT FILES!

#define MyAppName "testApp"
#define MyAppVersion "1.00"
#define MyAppPublisher "taichi"
#define MyAppURL "https://testApp.com/"
#define MyAppExeName "testApp.exe"

[Setup]
; NOTE: The value of AppId uniquely identifies this application. Do not use the same AppId value in installers for other applications.
; (To generate a new GUID, click Tools | Generate GUID inside the IDE.)
AppId={{xxx-xxxx-xxxxx-xxx}
AppName={#MyAppName}
AppVersion={#MyAppVersion}
;AppVerName={#MyAppName} {#MyAppVersion}
AppPublisher={#MyAppPublisher}
AppPublisherURL={#MyAppURL}
AppSupportURL={#MyAppURL}
AppUpdatesURL={#MyAppURL}
DefaultDirName={autopf}\{#MyAppName}
DisableProgramGroupPage=yes
; Uncomment the following line to run in non administrative install mode (install for current user only.)
;PrivilegesRequired=lowest
OutputDir=C:\Users\taichi\Desktop
OutputBaseFilename=testAppSetup
Compression=lzma
SolidCompression=yes
WizardStyle=modern
ArchitecturesInstallIn64BitMode=x64
ArchitecturesAllowed=x64

[Code]

/////////////////////////////////////////////////////////////////////
function GetUninstallString(): String;
var
  sUnInstPath: String;
  sUnInstallString: String;
begin
  sUnInstPath := ExpandConstant('Software\Microsoft\Windows\CurrentVersion\Uninstall\{#emit SetupSetting("AppId")}_is1');
  sUnInstallString := '';
  if not RegQueryStringValue(HKLM, sUnInstPath, 'UninstallString', sUnInstallString) then
    RegQueryStringValue(HKCU, sUnInstPath, 'UninstallString', sUnInstallString);
  Result := sUnInstallString;
end;

function GetUninstallString32: string;
var
  sUnInstPath: string;
  sUnInstallString: String;
begin
  Result := '';
  sUnInstPath := ExpandConstant('Software\Microsoft\Windows\CurrentVersion\Uninstall\{{A227028A-40D7-4695-8BA9-41DF6A3895C7}_is1'); { Your App GUID/ID }
  sUnInstallString := '';
  if not RegQueryStringValue(HKLM32, sUnInstPath, 'UninstallString', sUnInstallString) then
    RegQueryStringValue(HKCU, sUnInstPath, 'UninstallString', sUnInstallString);
  Result := sUnInstallString;
end;

/////////////////////////////////////////////////////////////////////
function IsUpgrade(): Boolean;
begin
  Result := (GetUninstallString() <> '');
end;

function IsUpgrade32(): Boolean;
begin
  Result := (GetUninstallString32() <> '');
end;

/////////////////////////////////////////////////////////////////////
function UnInstallOldVersion(): Integer;
var
  sUnInstallString: String;
  iResultCode: Integer;
begin
// Return Values:
// 1 - uninstall string is empty
// 2 - error executing the UnInstallString
// 3 - successfully executed the UnInstallString

  // default return value
  Result := 0;

  // get the uninstall string of the old app
  sUnInstallString := GetUninstallString();
  if sUnInstallString <> '' then begin
    sUnInstallString := RemoveQuotes(sUnInstallString);
    if Exec(sUnInstallString, '/SILENT /NORESTART /SUPPRESSMSGBOXES','', SW_HIDE, ewWaitUntilTerminated, iResultCode) then
      Result := 3
    else
      Result := 2;
  end else
    Result := 1;
end;

function UnInstallOldVersion32(): Integer;
var
  sUnInstallString: String;
  iResultCode: Integer;
begin
// Return Values:
// 1 - uninstall string is empty
// 2 - error executing the UnInstallString
// 3 - successfully executed the UnInstallString

  // default return value
  Result := 0;

  sUnInstallString := GetUninstallString32();
  if sUnInstallString <> '' then begin
    sUnInstallString := RemoveQuotes(sUnInstallString);
    if Exec(sUnInstallString, '/SILENT /NORESTART /SUPPRESSMSGBOXES','', SW_HIDE, ewWaitUntilTerminated, iResultCode) then
      Result := 3
    else
      Result := 2;
  end else
    Result := 1;
end;

/////////////////////////////////////////////////////////////////////
procedure CurStepChanged(CurStep: TSetupStep);
begin
  if (CurStep=ssInstall) then
  begin
    if (IsUpgrade()) then
    begin
      UnInstallOldVersion();
    end;
  end;
  begin
    UnInstallOldVersion32();
  end;
end;

[Languages]
Name: "english"; MessagesFile: "compiler:Default.isl"

[Tasks]
Name: "desktopicon"; Description: "{cm:CreateDesktopIcon}"; GroupDescription: "{cm:AdditionalIcons}"; Flags: unchecked

[Files]
Source: "C:\Users\taichi\Documents\hold\testAppDevelop\dist\testApp\testApp.exe"; DestDir: "{app}"; Flags: ignoreversion
                                                           

[Icons]
Name: "{autoprograms}\{#MyAppName}"; Filename: "{app}\{#MyAppExeName}"
Name: "{autodesktop}\{#MyAppName}"; Filename: "{app}\{#MyAppExeName}"; Tasks: desktopicon

[Run]
Filename: "{app}\{#MyAppExeName}"; Description: "{cm:LaunchProgram,{#StringChange(MyAppName, '&', '&&')}}"; Flags: runasoriginaluser nowait postinstall skipifsilent