When I wrote the sample script and the related blog post, it was quite clear that you should query the registry to detect previous installed software,
function InitializeSetup(): Boolean;
var
oldVersion: String;
uninstaller: String;
ErrorCode: Integer;
begin
if RegKeyExists(HKEY_LOCAL_MACHINE,
'SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{F768F6BA-F164-4599-BC26-DCCFC2F76855}_is1') then
begin
RegQueryStringValue(HKEY_LOCAL_MACHINE,
'SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{F768F6BA-F164-4599-BC26-DCCFC2F76855}_is1',
'DisplayVersion', oldVersion);
if (CompareVersion(oldVersion, '6.0.0.1004') < 0) then
begin
if MsgBox('Version ' + oldVersion + ' of Code Beautifier Collection is already installed. Continue to use this old version?',
mbConfirmation, MB_YESNO) = IDYES then
begin
Result := False;
end
else
begin
RegQueryStringValue(HKEY_LOCAL_MACHINE,
'SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{F768F6BA-F164-4599-BC26-DCCFC2F76855}_is1',
'UninstallString', uninstaller);
ShellExec('runas', uninstaller, '/SILENT', '', SW_HIDE, ewWaitUntilTerminated, ErrorCode);
Result := True;
end;
end
else
begin
MsgBox('Version ' + oldVersion + ' of Code Beautifier Collection is already installed. This installer will exit.',
mbInformation, MB_OK);
Result := False;
end;
end
else
begin
Result := True;
end;
end;
Your InstallShield based installer should also insert a GUID based subtree to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\
, so just analyze what has been there and take necessary actions to uninstall it.
A more recent blog post can be found here.